Ultraviolet-induced erythema is now recognized as an important clinical marker for skin cancer risk. People with a history of repeated erythematous exposures to sunlight are more likely to develop both melanoma1-3 and nonmelanoma skin cancers.4-6 Is erythema the most important thing we need to be concerned about in terms of protecting the public from the harmful effects of sunlight? What do we know about UV-induced erythema, and why is it a powerful influence on skin cancer risk?