In a retrospective analysis of patients receiving intraperitoneal radioactive colloidal chromic phosphate or colloidal gold the value of these substances in Stage I A ovarian cancer was assessed. In addition, complications of isotope therapy were analyzed in all patients receiving radioactive colloids for Stages I, II or III ovarian cancer. Ninety-four percent of those with Stage I A ovarian cancer were alive without evidence of recurrence after surgery plus radioactive colloids. In a small group (Stage I A) treated by surgery alone 22% were alive without evidence of malignancy. Of 74 women who received intraperitoneal radioactive colloids postoperatively only 1 sustained a moderately severe complication.