The purpose of this study was to evaluate the toxicity and antitumor activity of low doses of human lymphoblastoid interferon in 36 patients with measurable disease in whom higher priority treatment methods had failed. All but one had surgically confirmed advanced disease and had undergone initial treatment with a multiagent chemotherapeutic regimen in combination with cisplatin; four patients had also received radiation therapy. Their age range was 28 to 74 years. All had Gynecologic Oncology Group performance grade 2 or better (Karnofsky, 50% and above). Human lymphoblastoid interferon was administered at 5 megaunits/m2 intramuscularly, for 5 days per week (Monday through Friday) for 6 consecutive weeks. Patients who exhibited response or stable disease at 6 weeks were placed on a regimen of maintenance therapy at the same dose level for 2 days per week (Monday and Tuesday), for up to 12 months or until progression. Twenty-eight patients were evaluable for response: two with complete responses (7.1%), three with partial responses (10.8%), 14 with stable disease (50.0%), and nine with increasing disease (32.0%). Among the cumulative adverse effects, fatigue was most common, followed by moderate leukopenia and thrombocytopenia. Other observed adverse effects consisted of severe nephrotoxicity in two patients and myocardial infarction in one patient. It appears that therapy with human lymphoblastoid interferon may have cytostatic and possibly cytotoxic effects in this group of patients, with acceptable adverse reactions.