Originally Posted by
Rapt
I'd say that your best defense is to avoid situations where you're likely to encounter a bear. Take precautions with your food and other good smelling things (toothpaste, soap etc..) and where you prepare or use said things.
Pepper spray gets mixed results from the field, especially since its harder to use accurately than a gun. You sure want to be aware of wind direction since getting even a little blowing back at you is going to be REALLY unpleasant. Also remember that if people hyped on adrenaline can function after exposure then animals can too.
A good dog who stays WITH you and doesn't run off, after stuff is an extra deterrent. Especially if they "marK" around the camp area. Most animals will respect that barrier.
Gun choices vary. Shotguns with slugs are your BEST bet if you want to be certain. Otherwise something like a high power handgun is good 10mm, 45-08, ...
Being Canadian its quite difficult to get permission to carry a handgun, and of course its illegal to carry ANY gun in a park. So, we make do. I've seen bears when camping, but never been bothered.