Feasibility and the efficacy of mega-dose chemotherapy with peripheral blood stem cell transplantation (PBSCT) for small cell lung cancer (SCLC) were evaluated. Autologous peripheral blood stem cell (APBSC) was collected after induction chemotherapy (Extensive disease: CDDP+etoposide+ADM, Limited disease: CDDP+etoposide) followed by the administration of granulocyte colony stimulating factor (G-CSF). Five cases of ED and 2 cases of LD have been entered in the protocol so far. PBSC was harvested after the second course of induction chemotherapy, and a sufficient number of PBSC (CFU-GM > or = 1 x 10(5)/kg) could be harvested and cryopreserved in all 7 cases. After completion of 4 courses of induction chemotherapy, three patients who achieved CR or good PR were treated by the combination of CBDCA (1,600 mg/m2) plus etoposide (1,600 mg/m2) followed by APBSCT and G-CSF. Hematologic recovery after APBSCT was rapid (absolute granulocyte count > 500/microliters: 9-11 day, Plt > 3 x 10(4)/microliters:10-14 day) and no infectious episode nor bleeding tendency occurred throughout the treatment period. Although grade 3 gastrointestinal toxicity was seen in one patient, the mega-dose chemotherapy with APBSCT in SCLC was considered safe and feasible. Further clinical trials are needed to establish the role of mega-dose chemotherapy for the treatment of SCLC.