Twenty-two cases of keratin granulomas of the peritoneum associated with endometrioid adenocarcinoma with squamous differentiation of the endometrium, the ovary, or both, and with an atypical polypoid adenomyoma of the endometrium were reviewed. Follow-up data were available in 18 cases. Twelve patients were well and disease free 13 months to 15.2 years postoperatively; one patient died of unrelated disease 21 years postoperatively; three patients were tumor free with a short duration of follow-up; one patient, who had a stage Ic ovarian tumor, died of pulmonary embolism during the treatment of recurrent tumor 1 year after operation; and a final patient, who had been followed for 3 months after operation for stage IV disease, was alive with residual tumor. At least six patients with stage I carcinomas were treated with postoperative irradiation because the granulomas had raised a suspicion of advanced disease. Follow-up data on the patients in this series suggest that peritoneal keratin granulomas have no prognostic significance and should be distinguished from viable tumor implants on microscopic examination.