Frostbite is a local freezing injury that can cause tissue loss. Historically, it has been a disease of wars, but it is a hazard for anyone who ventures outdoors in cold weather. Frozen tissue is damaged both during freezing and rewarming. Frozen tissue is numb. Rewarming causes hyperemia and is often painful. Blisters and edema develop after rewarming. Hard eschar may form with healthy tissue deep to the eschar. Frostbite can be classified as superficial, without permanent tissue loss, or deep, with varying degrees of permanent tissue loss, often less than appearances suggest. It can be difficult to predict the amount of tissue loss at the time of presentation and early in the subsequent course. Prevention is better than treatment. It may be advisable not to rewarm frozen extremities in the field, but spontaneous thawing is often unavoidable. Extremities that have thawed should be protected from refreezing at all costs. Once in a protected environment, extremities that are still frozen should be rapidly thawed in warm water. Therapy with aspirin or ibuprofen may be helpful, but evidence is limited. Thrombolytic treatment within the first 24 hours after rewarming seems to be beneficial in some cases of severe frostbite. Prostacyclin therapy is very promising.