Seventy previously untreated patients with advanced NSCLC were randomised, after stratification for stage (IIIB vs. IV) and Performance Status (0-1 vs. 2), to receive either treatment A: CDDP 40 mg/m2 + VP16 100 mg/m2 day 1-3 (37 patients); or treatment B: CBDCA 250 mg/m2 day 1 + CDDP 30 mg/m2 day 2, 3 + VP16 100 mg/m2 day 1-3 (33 patients). Therapy was recycled on day 29 in both arms. The two arms were well balanced for the main pretreatment characteristics. Sixty-six patients (32 with Stage IIIB and 34 with Stage IV disease) were evaluable for toxicity and response (arm A = 34, arm B = 32), while four ineligible patients were excluded from analysis. Acute toxicity was assessed at recycling. Non-hematologic toxicity was higher in arm A. However, the reduction of nephrotoxicity (9% vs. 23%) in arm B was lower than expected. Leukopenia (15 vs. 5 patients) or thrombocytopenia (7 vs. 0 patients) of any grade affected more patients of arm B. Moreover, Grade 3-4 leukopenia (six patients) or thrombocytopenia (four patients) was observed only in arm B. Seventeen patients responded: 11/34 (32%; 95% C.I. = 17-50%) in arm A, and 6/32 (19%; 95% C.I. = 7-36%) in arm B. Median survival times of 40 and 34 weeks, respectively, were reported in arm A and B. Stage IIIB and squamous cell histology were associated with a higher probability of response. In conclusion, the partial replacement of CDDP with CBDCA in combination with VP16 slightly improves the tolerance of the treatment in terms of nephro- and neurotoxicity; however, it induces a significant increase in hematologic toxicity. In view of this unfavourable toxicologic profile and of the discouraging response rate observed, this regimen cannot be recommended as standard treatment in advanced NSCLC.