To evaluate the role of amphotericin B (AmB) in the biochemical modulation of antineoplastic agents, AmB was administered as a continuous infusion over a period of 52 to 120 h to 14 patients (26 courses) with advanced carcinomas. Continuous infusion amphotericin B (CI-AmB) was delivered at a rate of 0.5 to 0.8 mg/kg/d (19-31 mg/m2/d). The AmB plateau levels assayed by HPLC ranged from 0.7 to 1.9 micrograms/mL and were directly related to the infusion rate. The AmB plasma disposition was biphasic, with mean half-lives of 17 h for the first phase and 11 d for the terminal phase, and a mean residence time of 12 d. Biochemical modulation of antineoplastic agents (lomustine, doxorubicin, cyclophosphamide) by CI-AmB was not demonstrated clinically. Acute toxicities of fever and chills were noted in only 3 of the 26 courses. Reversible renal toxicity was observed in 23 courses. Therapeutic antifungal plasma levels were rapidly reached and maintained for the duration of infusion, with a reduction of acute toxicities associated with shorter infusions. These observations provide impetus for further clinical investigation of CI-AmB.