The term epidermal nevus syndrome is not suitable to describe an entity because there are different birth defects associated with epidermal nevi. A new classification is proposed to distinguish three well-defined syndromes, each recognizable by a different type of nevus. The sebaceous nevus syndrome and the Proteus syndrome are most likely due to autosomal lethal mutations and therefore always occur sporadically, whereas the CHILD syndrome can be transmitted from a mother to her daughter as an X-linked dominant, male-lethal trait. Moreover, the nevus comedonicus syndrome can be regarded as an entity closely related to this group of disorders. It may represent another autosomal lethal mutation that survives by mosaicism. In addition, several less well-defined phenotypes associated with epidermal nevi are reviewed. Some of them are regarded as entities in limbo.