Recent studies suggest that epidermal skin lipids play an important role in the pathogenesis of skin diseases associated with seborrhoea or sebostasis. Depending on the state of the skin, various lipids are found in varying quantities and proportions. In some sebostatic diseases, in particular, altered enzyme activities relevant to the synthesis of lipids have been identified, which may account for alterations in epidermal lipid fractions. This concept represents a substantial modification of earlier ones, according to which sebostatic or seborrhoeic skin diseases were attributed solely to decreased or increased sebum lipids, respectively. This provides an important rationale for a new approach to the therapy of certain skin diseases with specific lipid fractions, such as ceramides.