This communication represents the definitive report of a randomized phase III study comparing cisplatin and carboplatin, in combination with vindesine and mitomycin C in stage IIIB and IV squamous-cell bronchogenic carcinoma. A total of 221 patients entered the study and were randomized into two arms. Of these, 114 patients (109 evaluable for activity) were randomized to arm A, receiving cisplatin 120 mg/m(2), mitomycin C 8 mg/m(2) and vindesine 3 mg/m(2) per cycle; 107 patients (101 evaluable for activity) were randomized to arm B receiving carboplatin 500 mg/m(2) with the same doses of mitomycin C and vindesine per cycle. Patients with progressive disease (PD) were excluded from the study after the 2nd cycle, and those with stable disease (SD), partial response (PR) and complete response (CR) received six cycles of chemotherapy (or less in case of early progression). Patients were stratified according to the clinical stage (IIIB vs. IV), performance status (0+1 vs. 2+3) and tumor histological grade (I+II vs. III). In the cisplatin arm two patients (1.9%) achieved a CR, 38 (34.9%) a PR, 45 (41.2%) a SD and 24 (22.0%) had PD; the overall response rate was 40/109 (36.8%). In the carboplatin arm five patients (5.0%) achieved a CR, 31 (30.7%) a PR, 40 (39.6%) a SD, and 25 (24.7%) had PD; the overall response rate was 36/101 (35.7%). No statistically significant difference in response rate was present between the two arms, and the response rate was not influenced by performance status, histological grade or clinical stage. The Kaplan-Meyers curves displayed a significant advantage both for time to progression (P=0.005) and overall survival (P=0.008) for patients in the carboplatin arm. The advantage for patients receiving carboplatin instead of cisplatin appeared evident in univariate setting for patients with a good performance status and clinical stage IV, and occurred irrespectively of tumor histological grade; response duration and survival of responders was identical in the two arms. Patients achieving a stable disease survived longer in the carboplatin than in the cisplatin arm (P=0.012). Thus, substitution of cisplatin by carboplatin in the combination chemotherapy regimen, although more hematologically toxic (but less emetogenic) resulted in a similar response rate, but a significantly longer time to progression and overall survival.