The best way to reduce the risk of being attacked is to understand bear behavior and avoid doing things that might provoke the bears (getting too close to their cubs, stowing food improperly in camp, etc.). However, if you do encounter a charging grizzly bear, the first defense is, interestingly enough, pepper spray. More often than not, the charge is either a bluff or simply an attempt to drive off a threat, rather than an actual attack, and pepper spray has proven effective in driving away bears without harm to either the bear or the human. If you're armed, your weapon is a second choice, with two big disadvantages compared to pepper spray: If the bear is bluffing, it may be killed needlessly; and if you miss, you may turn a bluffing bear into an enraged bear and be killed needlessly.

If you have neither of these, or if they've failed to deter the bear and it continues to charge, lie face-down or roll into a ball, protect your head and neck, and move as little as possible. If the bear doesn't see you as a threat, it will most likely leave you alone. However, if it continues to attack, defend yourself using whatever weapons are available, aiming for the bear's head, eyes, and snout. Don't run away (it can trigger a chase response, and grizzly bears can run early twice as fast as humans), and climbing a tree is risky (they can reach more than 10 feet up while standing on the ground, and some grizzlies can climb).

The exception to the passive approach is if a grizzly bear enters your campsite. These bears are more likely to have lost their fear of humans and now recognize us as potential sources of food. If you have pepper spray, use it; if not, and the bear charges, you have little choice but to attack, again aiming for the eyes and nostrils.