In the course of a cesarean section on a 38-yr-old negroid patient the peritoneum was found to be studded with small greyish white nodules resembling carcinomatosis peritonei. On microscopical examination these appeared to be composed of decidualized cells and smooth-muscle cells. No evidence of malignancy was observed. Another 18 cases of leiomyomatosis peritonealis disseminata have been reported previously in the literature. It seems likely that these small tumors originate from subcelomic mesenchymal cells which, through a process of metaplasia, differentiate into myofibroblasts under the influence of hormonal factors. At laparoscopy, performed several years before the patient's pregnancy, the peritoneum was observed to be entirely normal. Regression of the nodules was evident at laparoscopy 12 wk post partum.