The aim of this study was to evaluate the safety and the biological effects of interleukin (IL-1 alpha) in patients' with recurrent ovarian carcinoma treated with carboplatin. In this phase I study, IL-1 alpha was administered by a continuous intravenous infusion at doses ranging 0.1-10 micrograms/m2 every 24 h for 4 days (96 h) 3 weeks before the first dose of carboplatin (400 mg/m2) in patients with potentially platinum-sensitive ovarian cancer. The maximum tolerated dose was 3 microgram/m2/day. Dose-limiting effects at 10 micrograms/m2/day were fever, chills, hypotension and fluid retention. Minor but objective antitumour effects were observed in 2 of 18 patients. 4 patients (including 1 with a minor response) had a decrease of the CA-125 serum level ranging from 33 to 39%. The trial design precluded evaluation of the duration of response to single-agent IL-1 alpha. Based on this trial design, there is evidence of minor antitumour effect to a single course of IL-1 alpha dose given prior to chemotherapy.