A weekly, intensive chemotherapy regimen has been used to treat 70 patients with small-cell lung cancer (SCLC). Forty-five patients had limited disease (LD) and 25 extensive disease (ED) with good prognostic features. The regimen consisted of cisplatin 50 mg/m2 intravenously (IV) day 1 and etoposide 75 mg/m2 IV days 1 and 2, alternating weekly with ifosfamide 2 g/m2 IV day 8 and doxorubicin 25 mg/m2 IV day 8, for a total of 12 weeks. Dose modifications were made according to defined hematologic criteria. Responding patients with limited disease subsequently received mediastinal radiotherapy. Overall response to chemotherapy was 91% with a complete response (CR) rate of 50%. Forty-five patients with limited disease (LD) achieved an overall response rate of 91% with a CR rate of 51%, and 25 patients with extensive disease (ED) achieved an overall response rate of 92% with a CR rate of 48%. Median survival for the whole group was 54 weeks (LD, 58 weeks; ED, 42 weeks). Hematologic toxicity was predictable, without the wide fluctuations in WBC count seen in conventional 3-weekly regimens. In all, one quarter of treatment courses were delayed, most frequently because of leukopenia. Dose reductions were required in 63% of cases. The average delivered dose intensity was calculated and shown to be 73% of projected. Nonhematologic toxicity was mild with nausea and vomiting being the most common. This weekly schedule of chemotherapy has proved to be active and well tolerated and is currently being compared with conventional 3-weekly chemotherapy in a randomized study.