Madelung's disease is a rare benign disorder characterized by symmetrical deposition of adipose tissue on the neck and shoulders. The cause of Madelung's disease is obscure and may be associated with mitochondrial dysfunction. In this communication, we report two cases encountered at Cardinal Tien Hospital during 1992. Besides physical check-up and laboratory examination, adipose tissue and muscle biopsies from the biceps brachii were performed. As lipid metabolism is closely related to mitochondrial respiration, biochemical studies may be of great value in clarifying the pathogenetic mechanism of Madelung's disease. We thus determined the activities of mitochondrial respiratory enzymes (NADH cytochrome c reductase, succinate cytochrome c reductase, cytochrome c oxidase) in muscle and blood cells and revealed that the electron transport functions were all elevated. Molecular analysis of mitochondrial DNA from the muscle and blood cells of both patients failed to find large-scale deletion or point mutations.