Between September 1968, and December 1975, 40 patients with Stage II epithelial tumors of the ovary were treated at the Joint Center for Radiation Therapy. Thirty-six patients had undergone a total abdominal hysterectomy and bilateral salpingo-oophorectomy (BSOH) with attempted total removal of disease, and all patients received postoperative pelvic irradiation. The five-year actuarial relapse-free survival rate is 66% and the overall survival rate 70% for the entire group of patients. The histology was reviewed in all cases and graded for the percentage of solid vs. papillary or glandular in the specimen. Of the 36 patients treated with a BSOH, 18 had well-differentiated tumors defined as containing less than a 10% solid architectural pattern. There have been no relapses in this group of patients. In contrast, 9 of 18 patients with moderately or poorly differentiated tumors containing a 10% or more solid pattern have relapsed; five diffusely in the abdomen, two in the pelvis, and two in the lungs or pleura. It appears that a BSOH followed by pelvic irradiation is sufficient treatment for Stage II patients with well-differentiated tumors showing less than a 10% solid pattern. In contrast, patients with less well-differentiated tumors have a high risk of relapse outside of the pelvis and need additional treatment. Alternative treatment options are discussed.