Because of potential synergistic interactions, we added 25 mg/m2 i.v. cisplatin (P) 25 given on days 1-5 to the combination of 45 mg/m2 i.v. doxorubicin (A) given on day 1, 800 mg/m2 i.v. cyclophosphamide (C) given on day 1, and 50 mg/m2 i.v. etoposide (E) given on days 1-5. The resulting PACE regimen was given every 21 days for the first three courses and then every 28 days for the next five courses. PACE was used in two trials: the first, for both limited and extensive disease, was conducted at the University of Maryland Cancer Center and North Shore University Hospital; and the second, for extensive disease, was carried out as a Cancer and Leukemia Group B pilot study. Chest irradiation was not used. Prophylactic cranial irradiation at a dose of 3,000 cGy was given to all patients achieving a complete response (CR). A total of 33 subjects were entered in the first study; 8 of the 15 (53%) presenting with limited disease and 7 of the 18 (39%) exhibiting extensive disease achieved a CR. A partial response (PR) was obtained in 27% and 33% of cases, respectively. Of the 34 patients entered in the second study, 25 were eligible; 8 (32%) achieved a CR and 6 (24%) showed a PR. Toxicity was severe in both studies, including greater than 90% severe or life-threatening leukopenia and thrombocytopenia. Serial creatinine-clearance evaluations in the first study indicated progressive deterioration, which required discontinuation of the cisplatin before the planned completion of treatment in most cases. Since the response rate was no higher than the historic data reported for the three-drug ACE combination and because the toxicity was severe, the studies were stopped and patients were followed for survival. After a follow-up period of greater than 6 years, the median survival was 24 months for limited disease, with 33% and 27% of the patients being alive at 3 and 6.5 years, respectively. The median survival for extensive disease was 15 and 11 months in the first and second studies, respectively. These pilot studies suggest that the addition of cisplatin may augment the activity of the ACE regimen, but at the cost of severe toxicity. Further studies seem warranted if the myelotoxicity can be better controlled.