If you are going on a hike what should you take in your first-aid kit?

The following items were taken from the Official Boy Scout web site: www.scouting.org

For some really good information I suggest that you go to their site.

It is important that one person in each touring group be trained in the principles of first aid, know how and when to put this knowledge to the best use, and thoroughly understand the limitations of this knowledge.

Bar of soap

2-inch roller bandage

• 1-inch roller bandage
• 1-inch adhesive
• 3-by-3-inch sterile pads
• Triangular bandage
• Assorted gauze pads
• Adhesive strips
• Clinical oral thermometer
• Scissors
• Tweezers
• Sunburn lotion
• Lip salve
• Poison-ivy lotion
• Small flashlight (with extra batteries and bulb)
• Absorbent cotton
• Water purification tablets (iodine)
• Safety pins
• Needles
• Paper cups
• Foot powder
• Instant ice packs

Recommended Enhancements:

• If 1" Roller Bandage is an Ace Wrap I'd go to 3". You can use 3" for places 1" won't work but not vice versa. If they mean 1" gauze wrap I'd skip it altogether -- see the KoBan below.
• I'd swap 1" adhesive for 1" or 2" KoBan. Great stuff -- doesn't stick to wounds, can be trimmed to size, weighs less.
• I personally like 4"x4" sterile pads -- matter of taste.
• Skip the triangular bandage; that's what your bandanna is for. Likewise, if you need one they're easily improvised from a T-shirt.
• Clinical Oral Thermometer as long as it's not glass. Glass thermometers tend to break in the field.
• Poison-ivy doesn't typically show up for 48 hours or so, and for some folks it doesn't work well. Also, depending on where you hike, this vegetation may not exist or may be seasonal. Unless you're going to be out there for a few days in an area where this is a problem, consider skipping this -- more heavy goop to mess up your kit. If you really need something for this purpose. go with a general purpose pain salve (xylocaine, lidocaine, etc.).
• Flashlights are great -- make it a waterproof one and don't skimp. MagLite makes a great one, but so do others. Get one of that quality.
• Skip the absorbant cotton balls; use a torn up sterile pad for that. These wad up over time, get dirty (unless you put them in a container -- more weight), and what do you do with them?
• Skip the needles; use the safety-pins for that. Stowing a needle is a royal pain. If you worry about such things, bring a cobbler's awl so you have your needles and can sew broken boots back together. Overkill I think but better than a needle by itself.
• Skip the paper cups -- there's no use for them -- just something else to get soggy. Many hikers carry a Yosemite cup wherever they go. In a pinch, these can be heated over a small fire as well, and these make dipping from streams a snap.
• I don't carry foot powder myself as I wash my feet a LOT on the trail, and carry extra socks. If you're going for only a few days, this may be extra weight.
• Instant ice packs are usually a waste of time. While I'm a huge fan of coldpacking nearly any injury I run into, chemical cold packs don't get very cold at all, are expensive and very heavy, and a danger if you puncture them. If you have a cold stream or even a good breeze and a wet bandanna, you can get nearly the same effect.
• I'd add the following:
• ** Pencil
  • 1-2 sheets of waterproof paper -- DayGlo is good.
  • Waterproof matches or flint and steel (extra set in the first aid kit).
  • Moleskin (maybe the most useful thing on the trail for tenderfoots!).
  • Small Nalgene type bottle of hydrogen peroxide 3%-- 3oz. should do.
  • Bubble pack of Ibuprofen -- works for pain and fevers. No need for that thermometer if you can't treat the fever.
  • Bubble pack of Benadryl/diphenhydramine -- good for stings and allergies. Doubles as a sleeping med. Been around forever -- safe and tested.
  • Salt Tabs (everyone argues this one. I like it for Heat Exhaustion to keep it from turning into Heat stroke).