One hundred nine previously untreated patients with small cell lung cancer were treated for five consecutive days with 20 mg/m2/day of cisplatin and 600 mg/m2/day of 5-fluorouracil. One cycle of chemotherapy was administered every three weeks. The patients received a median number of three cycles. Then they were transferred to CAE chemotherapy. A 77% overall response rate (95% confidence interval of 0.70-0.85) was observed after initial cisplatin-5FU treatment. Twenty-three complete responses (21%) and 62 partial responses (56%) were obtained. In cerebral metastases the response rate was high at 91% (21 out of 23), with 43% complete responses. In the limited forms, statistical survival at 1 year was 25%. A Grade 3-4 thrombocytopaenia was observed in 10 patients (9%) and a Grade 2-3 leukopaenia in four patients. Three patients suffered from a Grade 2 cardiac toxicity. The cisplatin-5-fluorouracil combination demonstrates promising initial response rate in small cell lung cancers. Its main interest is in its important action on cerebral metastases and its moderate haematological toxicity.