Hydroa aestivale is characterized by the occurrence during the spring and summer months of polymorphous lesions on the exposed skin of persons who are usually in the younger age group. The lesions include macules, papules, vesicles, blebs, eczematous patches, and wheal-like areas, and the sites of predilection are the face, ears, neck, hands, and forearms. Several separate areas of skin are usually involved rather than diffuse involvement of large exposed regions. Some of the lesions, especially the blebs, become crusted and heal with vaccinia-like scars. Although there is some controversy in regard to the sex incidence,* males seem to predominate.5 The disorder frequently improves or disappears at puberty although persistence into the fourth or fifth decade has been recorded. (We suspect that some of the older patients may have had porphyria.) Another symptom complex, hydroa vacciniforme, is regarded by some authors as only a more severe form of hydroa