1. Navigation
2. Sun protection
3. Insulation (extra clothing)
4. Illumination
5. First-aid supplies
6. Fire
7. Repair kit and tools
8. Nutrition (extra food)
9. Hydration (extra water)
10. Emergency shelter

1. Map
2. Compass
3. Sunglasses and sunscreen
4. Extra clothing
5. Headlamp/flashlight
6. First-aid supplies
7. Firestarter
8. Matches
9. Knife
10. Extra food

The original Ten Essentials list was assembled in the 1930s by The Mountaineers, a Seattle-based organization for climbers and outdoor adventurers. The group's updated "systems" approach made its debut in the seventh edition of its seminal text on climbing and outdoor exploration, Mountaineering: The Freedom of the Hills (The Mountaineers Books, 2003).

Why create such a list? The book's editors explain: "The purpose of this list has always been to answer two basic questions: First, can you respond positively to an accident or emergency? Second, can you safely spend a night—or more—out?"

Packing these items whenever you step into the backcountry, even on day hikes, is a good habit to acquire. True, on a routine trip you may use only a few of them. Yet you'll probably never fully appreciate the value of the Ten Essentials (or the wisdom that went into building the list) until you really need one of them.

1. Navigation

Map and compass are now viewed as two components of a navigation system. Add a wrist altimeter, toss in a GPS and, well, you can see how the systems approach to the Ten Essentials can easily total more than 10 individual items.

A topographic map (in a protective sheath or case) should accompany you on any trip that involves anything more than a short, impossible-to-miss footpath or frequently visited nature trail. Handout maps, the type offered at visitor centers or entrance stations, usually provide only simplistic line drawings of trails and do not show the topographic details necessary for route finding. If, for example, you stray off the trail or need to locate a water source, you need a topo map.

For more details, see How to Choose a Map

A compass, combined with map-reading knowledge, is a vital tool if you become disoriented in the backcountry. Have high-tech GPS receivers make compasses, with a history that dates back to 12th century Europe, obsolete? No. A compass weighs next to nothing and does not rely on batteries. So even if you're a techie who relies heavily on a GPS for navigation, a traditional compass is an indispensable backup. Note: A compass equipped with a sighting mirror can also be used to flash sunlight to a helicopter or rescuer during an emergency.

Learn more in How to Choose a Compass.

An altimeter is a worthwhile navigational extra to consider. It uses a barometric sensor to measure air pressure and provide a close estimate of your elevation—information that helps you track your progress and determine your location on a map. We say "estimate" because when weather changes, air pressure changes, and such a change can cause an altimeter's elevation reading to fluctuate even if it remains stationary.

If you travel regularly in the wilderness, consider taking a class to learn navigation techniques in depth.

2. Sun Protection

This involves sunglasses, sunscreen (for skin and lips) and, for optimized protection, lightweight, skin-shielding clothing.

Sunglasses are indispensable, and you'll need extra-dark glacier glasses if you're planning prolonged travel on snow or ice. All sunglasses sold at REI block 100% of ultraviolet light (UVA and UVB)—a key function of quality lenses. UVB rays, the rays that can burn your skin, have been linked to the development of cataracts.

Wraparound lenses keep light from entering the corners of your eyes and also help buffer eyes from wind. Factors influencing your choice of sunglasses include lens types, frames, fit and, of course, fashion. For details, see How to Choose Sunglasses.

When choosing sunscreen, health experts advise choosing 1) a formula that offers a sun protection factor (SPF) of least 15, though SPF 30 is recommended for extended outdoor activity and 2) one that blocks both UVA and UVB rays.

A sunscreen's SPF number refers only to its ability to absorb sunburn-causing UVB rays; measuring how it performs against age-inducing UVA rays is a topic under discussion at the Food and Drug Administration. Active ingredients considered most effective against UVA light are avobenzone, ecamsule, zinc oxide and titanium dioxide.

The biggest mistake people make with sunscreen? Applying too little, dermatologists say. A thin application diminishes the intended benefit of your chosen SPF. So glop it on, one ounce is needed to cover the arms, legs, neck and face of the average person. Depending on many factors (time of day, sweat and more), you should reapply as often as every two hours. And don't overlook SPF-rated lip balm.

For our full discussion on the topic, check out How to Choose Sunscreen.

Lightweight synthetic clothing often comes with an ultraviolet protection factor (UPF). Skin-care experts say using clothing to shield your skin is a good sun-protection strategy. Your activity level (and resulting perspiration) and the temperature are two key factors that will determine if you choose to wear pants or shorts (or long sleeves vs. short sleeves) while outdoors. You'll still need sunscreen for your face, neck and hands.

3. Insulation

Conditions can abruptly turn wet, windy or chilly in the backcountry, so it's smart to carry an additional layer of clothing in case something unexpected (you get hurt or lost, for example) prolongs your exposure to the elements.

The authors and editors of Mountaineering suggest this strategy: "Extra clothing should be selected according to the season. Ask this question: What is needed to survive the worst conditions that could be realistically encountered on this trip?"

Common options include a layer of underwear (tops and bottoms), an insulating hat, extra socks and a synthetic jacket or vest. And yes, humans lose significant heat through their heads. Thus, according to Mountaineering, it's smart to pack a hat or balaclava "because they provide more warmth for their weight than any other clothing article."

4. Illumination

Headlamps are the light source of choice in the backcountry. Reasons:

• Hands-free operation (their No. 1 advantage over flashlights)
• Low weight
• Compact size (so they occupy minimal space in your pack)
• Long battery life (in models using light-emitting diodes, or LEDs)

High-output LEDs (the 1- and 3-watt varieties) provide light output that is comparable to the output of incandescent bulbs, even those that use pressurized gas (xenox, halogen and other intensity-boosting gases). Because LEDs can handle rugged use (no filaments to break), offer vastly superior battery life and are perpetually evolving to higher levels of performance, it is quite likely most, and maybe all headlamps will be LED models.

It's easy to over-extend your stay on a picture-perfect mountain. If you're trying to hustle out of the backcountry in dwindling light or trying to set up camp as the last bit of blue drains from the sky, a headlamp is an invaluable aid.

Many headlamps also offer a strobe mode. It's a great option to have for emergency situations. Headlamps offer their longest battery life while in strobe mode.

Flashlights and packable lanterns also have value. Some flashlights cast very powerful beams and are useful for signaling during emergencies.

Always carry spare batteries—and if your light is equipped with an incandescent bulb, also carry spare bulbs. Every member of a backcountry party should carry his or her own light.

Evaluating lights (for battery life, the distance a beam throws "usable light," brightness attributes and more) can be a surprisingly detailed process. We do our best to simplify the discussion and guide you to the most meaningful numbers in our article How to Choose Headlamps.

5. First-aid Supplies

Pre-assembled first-aid kits take the guesswork out of building your own kit, though many people personalize these kits to suit individual needs. Any kit should include treatments for blisters, adhesive bandages of various sizes, several gauze pads, adhesive tape, disinfecting ointment, over-the-counter pain medication, pen and paper. Latex gloves also deserve consideration. The length of your trip and the number of people involved will impact the contents of your kit.

It's a good idea to carry some sort of compact guide to dealing with medical emergencies. Consult our guide How to Choose a First-Aid Kit.

6. Fire

Matches headed into the backcountry should be the waterproof variety, or they should be stored in a waterproof container. Take plenty and ensure they are kept dry. Convenience-store matchbooks are often too flimsy and poorly constructed to be trusted for wilderness use. Save yourself some frustration and tote reliable matches on every trip. Mechanical lighters are handy, but always carry some matches as a backup.

Firestarter, as the name implies, is an element that helps you jump-start (and possibly sustain) a fire. Of all the classic Ten Essentials, it is probably the one least commonly carried by wilderness travelers. But should you get stranded overnight in the boonies and you start to shiver, you need the means to build an emergency fire.

The ideal fire starter ignites quickly and sustains heat for more than a few seconds. Candidates include dry tinder tucked away in a plastic bag; candles; priming paste; heat "nuggets" (chipped-wood clusters soaked in resin). Even lint trappings from a household clothes dryer can work.

7. Repair Kit and Tools

Knives or multi-tools are handy for gear repair, food preparation, first aid, making kindling or other emergency needs. A basic knife should have at least one foldout blade (more likely two), one or two flathead screwdrivers, a can-opener and (though some people will call this a luxury) a pair of foldout scissors. The more complex your needs (if, for example, you are leading an inexperienced group), the more options you may want in your knife or tool. Read our tips for selecting knives and tools.

If you carry a self-inflating mattress, you probably do not carry a repair kit for it. Typically, the only people who do are those who have endured a puncture deep in the backcountry. Depending on your outlook on Murphy's Law, it's an item worth considering.

Here's a classic tip for carrying the basics of a poor-man's repair kit: Wrap strips of duct tape (the universal fix-it product) around your water bottle or trekking poles so you can repair who-knows-what in the backcountry.

8. Nutrition (extra food)

Always pack at least one extra day's worth of food. It can be as simple as a freeze-dried meal, but it's even smarter to include no-cook items with nearly infinite storage times: extra energy bars, nuts, dried fruits or jerky.

The process of digesting food helps keep your body warm, so on a cold night it's smart to munch some food before bunking down—just don't leave animal-attracting leftovers inside your shelter.

9. Hydration (extra water)

Mountaineering suggests always carrying at least one water bottle and a collapsible water reservoir. You should also carry some means for treating water, whether it is a filter/purifier or chemical treatment.

When beginning extended travel along a ridgeline or in alpine conditions, it's wise to consult your map and try to envision possible water sources. Try to resupply at the last obvious water source before beginning a stretch of unpredictable water availability.

10. Emergency Shelter

Shelter is a new component in the updated Ten Essentials, one that seems targeted at day trippers. (Most overnight wilderness travelers already carry a tent or tarp.) The thinking is, if getting lost or injured leaves you stranded in the backcountry, something is better than nothing if you have to deal with wind or rain. Options include an ultralight tarp, a bivy sack, an emergency space blanket (which packs small and weighs just ounces), even a large plastic trash bag.

Beyond the Top Ten

Earlier we mentioned an altimeter as worthy candidate to consider as an add-on to the updated Ten Essentials list. Here are a few others:

• Insect repellent: We break down the latest options for you in our well-researched article How to Choose Insect Repellent.
• Whistle: For summoning help; it will outlast your vocal chords.
• Ice ax: For safety when crossing snow fields.
• Communication device: Two-way radio, cell phone, satellite telephone; read our overview of the topic in How to Choose Two-Way Radios.
• Knowledge: Having items in your pack has no value unless you understand how to use them. As one search-and-rescue leader told us, "People talk about the Ten Essentials, but the most important essential is between your ears."

Final Thought

Even though you may only occasionally use a few of these items, carrying the Ten Essentials on all your backcountry excursions is a smart move. They serve as the antidote to the unexpected, like the seatbelts in your vehicle.

The Ten Essentials can also form the core of your home (or car) emergency-preparedness kit. They are all about safety, advance preparation and peace of mind. They could potentially save your life.

Contributor: T.D. Wood, REI's far-hiking Expert Advice editor.

Last updated: October 2007