A pilot study was conducted in which 15 patients with small cell lung cancer (SCLC) with limited or extended disease were treated with high dose etoposide (600 mg/m2 daily for 3 consecutive days) followed by autologous bone marrow transplantation (ABMT). Twelve patients underwent a double graft. All had achieved complete or partial remission with conventional induction chemotherapy (adriamycin and etoposide, plus cisplatin in five cases). After ABMT six of the 15 patients did not receive radiotherapy to the chest; all but four patients received prophylactic brain irradiation. No toxic deaths were recorded during the period of aplasia. Eleven patients relapsed and died after ABMT. The median time to death was 18 months. One other patient died at 13 months of unknown cause. At the present time three patients are alive and free of disease at 54, 51 and 47 months respectively. This pilot study shows that high dose etoposide and ABMT is well tolerated as late intensification for responsive SCLC. Definite conclusions about its precise role in therapy cannot yet be drawn.