A rare case of leiomyomatosis Peritonealis Disseminata (L.P.D.) associated with an Endometriosis is reported. A 40 years old non-gravid patient had a laparotomy for uterine fibromas. Multiple sub peritoneal nodules were found and a total hysterectomy with annexectomy was done with the diagnosis of peritoneal metastatic disease. The light and electron microscopy showed a benign multicentric proliferation of myofibroblasts and smooth muscles cells. The association with endometriosis suggests that L.P.D. must have a metaplastic origin, from subcoelomic mesenchymal cells, as speculated by previous authors.