Since 1980, 75 patients with small-cell lung cancer (SCLC) have been entered into four consecutive studies of high-dose chemotherapy using autologous bone marrow transplantation (ABMT) to assist haematological recovery. In the first study, 25 patients were treated with cyclophosphamide (160-200 mg/kg) as the sole chemotherapy; in the second (26 patients), the cycle of high-dose cyclophosphamide (with or without 800-1,200 mg/m2 etoposide) was repeated as induction treatment. In the first study, response was high [14 complete responses (CR), 7 partial responses (PR)] but was not increased by repeating the cycle (15 CR, 8 PR), and survival was slightly worse in the second trial. In the third study, 15 patients were treated with doxorubicin, vincristine and etoposide for two cycles and then with 200 mg/kg cyclophosphamide. Although high-dose cyclophosphamide increased the complete response rate, the additional responses were short-lived. In the final study, an attempt was made to increase the initial CR rate by combination chemotherapy using carboplatin (400-600 mg/m2), etoposide (120 mg/m2 x 4) and either high-dose cyclophosphamide (40 mg/kg x 4) or melphalan (140 mg/m2). Although all nine patients responded, none underwent a CR. The long-term survival (up to 7 years) does not appear to be different from that in comparably selected cases treated with conventional chemotherapy.