Small cell lung cancer usually responds to radiation and chemotherapy, but cures are infrequent. Autotransplantation attempts to increase cures by intensifying the effects of chemotherapy. We studied 103 patients receiving high-dose chemotherapy with autologous hematopoietic stem cell transplantation (SCT) for small cell lung cancer in 1989-1997 at 22 centers participating in the Autologous Blood and Marrow Transplant Registry. Median age at transplantation was 50 years (range, 30-74 years). Fifty-five percent of patients were men. Forty-seven percent of patients underwent transplantation in 1989-1993 and 53% in 1994-1997. Most patients received peripheral blood stem cells alone (39%) or with bone marrow (44%); 18% received bone marrow alone. The 2 most common preparative regimens were cyclophosphamide/carmustine/cisplatin (CBP) (60%) and ifosfamide/carboplatin/etoposide (ICE) (28%). Median time from diagnosis to transplantation was 6 months (range, 1-34 months). Most patients underwent transplantation after partial response (66%) or complete response (27%) to combination therapy. The 100-day mortality was 11% (95% confidence interval [CI], 6%-18%). Three-year probabilities of survival and progression-free survival (PFS) were 33% (95% CI, 24%-44%) and 26% (95% CI, 17%-36%), respectively, for all patients. Factors negatively associated with outcome in multivariate analysis were age greater than 50 years, extensive-stage disease at presentation, and preparative regimens other than CBP or ICE. Three-year survival and PFS rates were higher in patients with limited versus extensive disease, 43% versus 10% (P < .001) and 35% versus 4% (P < .001), respectively. Patients older than 50 years had nearly twice the risk of death or progression as younger patients (relative risk, 1.7; 95% CI, 1.1-2.8). Autologous SCT produces long-term survival in some patients with small cell lung cancer; SCT outcomes appear better in young patients with limited-stage disease. Transplantation for patients with extensive disease does not appear to produce substantial benefit.