The synergistic combination of cisplatinum and etoposide appears as the best second line treatment in patients relapsing from small cell lung carcinoma (SCLC). In order to test the dose-effect relationship of cisplatinum and etoposide in this situation, we have performed a randomised phase II trial comparing 2 five-day regimens: cisplatinum 20 mg/m2/day+etoposide 60 mg/m2/day (arm A) versus cisplatinum 40 mg/m2/day+etoposide 100 mg/m2/day (arm B) every 4 weeks. Thirty-seven patients were included (arm A: 18, arm B: 19), and 32 were considered to be eligible (arm A: 15, arm B: 17). Eight patients were non evaluable, five of them because of toxic death occurring prior to the second course (arm A: one from neutropenia; arm B: three from neutropenia and one from thrombopenia). The two groups were well balanced with regard to the main prognostic factors (age, sex, performance status, LDH level, response to induction chemotherapy). An objective response was observed in 10/24 evaluable patients (arm A: 4, arm B: 6) and was considered as complete in one patient in arm A and in 2 pts in arm B; these two patients presented with cerebral metastases and their response lasted 9 and 15 weeks respectively. The mean duration of response was 11 weeks in arm A and 10.5 weeks in arm B. The median actuarial survival of the overall population of eligible patients was 15 weeks: 13 weeks in arm A and 16.5 weeks in arm B. The study was discontinued because of the 23.5% toxic deaths rate in the high doses arm in this heavily pre-treated population of patients. However, the high response rate (54% overall, 35% considering toxic death as a failure) is impressive and presents evidence for the dose/effect relationship in SCLC.