Sixteen patients who underwent surgery and postoperative chemotherapy for carcinoma of the ovary were studied. Eleven survived more than 18 months without evidence of recurrence, and 5 died more than 5 months after surgery. Serial determinations were made preoperatively and postoperatively of the immunosuppressive effect of the serums of these patients on the response of normal lymphocytes to phytohcmagglutinin stimulation. These determinations were plotted for each patient; the shapes of the curves for patients who survived are markedly different from those of patients who died. The prognostic value of these findings is discussed.