A phase I trial was designed to examine the feasibility of combining interferon and Taxol with intraperitoneal radioimmunotherapy (177Lu-CC49). Patients with recurrent or persistent ovarian cancer confined to the abdominal cavity after first line therapy, Karnofsky performance status >60, adequate liver, renal and hematologic function, and tumor that reacted with CC49 antibody were enrolled. Human recombinant alpha interferon (IFN) was administered as 4 subcutaneous injections of 3 × 106U on alternate days beginning 5 days before RIT to increase the expression of the tumor-associated antigen, TAG-72. The addition of IFN increased hematologic toxicity such that the maximum tolerated dose (MTD) of the combination was 40 mCi/m2compared to 177Lu-CC49 alone (45 mCi/m2). Taxol, which has radiosensitizing effects as well as antitumor activity against ovarian cancer, was given intraperitoneally (IP) 48 hrs before RIT. It was initiated at 25 mg/m2and escalated at 25 mg/m2increments to 100 mg/m2Subsequent groups of patients were treated with IFN + 100 mg/m2Taxol + escalating doses of 177Lu-CC49. Three or more patients were treated in each dose group and 34 patients were treated with the 3-agent combination. Therapy was well tolerated with the expected reversible hematologic toxicity. The MTD for 177Lu-CC49 was 40 mCi/m2when given with IFN + 100 mg/m2Taxol. Interferon increased the effective whole body half-time of radioactivity and the whole body radiation dose. Taxol did not have a significant effect on pharmacokinetic or dosimetry parameters. Four of 17 patients with CT measurable disease had a partial response (PR) and 4 of 27 patients with non-measurable disease have progression-free intervals of 18+, 21+, 21+, and 37+ months. The combination of intraperitoneal Taxol chemotherapy (100 mg/m2) with RIT using 177Lu-CC49 and interferon was well tolerated, with bone marrow suppression as the dose-limiting toxicity. © 2001 Mary Ann Liebert, Inc.