Disseminated peritoneal leiomyomatosis is an unusual condition characterized by the development of numerous nodules in the peritoneal cavity which histologically have the appearance of smooth muscle tumors. The ninth proven case of this ill-understood disorder is presented here, with comments on some of the other published instances. Most reported cases were diagnosed in pregnant women, and there is good reason to believe that endocrine factors are of importance in the development of this condition. Attention is drawn to experimental studies in which an apparently similar condition has been produced in guinea pigs by endocrine manipulation. Clinically, the condition appears to be benign and the correct diagnosis is, therefore, of great importance. In the case presented here histological involution of the leiomyomatous peritoneal nodules could be demonstrated for the first time by two biopsies at an interval of 4 months--in the absence of any therapy apart from the termination of pregnancy.