Autologous bone marrow- and blood progenitor cell transplantation was performed in 130 patients with multiple myeloma in 16 European centers between 1986 and 1993. At the time of follow-up, 77 patients were alive and 53 were dead. Complete remission after transplantation was obtained in 47% of all patients. The actuarial survival at 65 months was 28%. The median duration of relapse-free survival among patients who were in complete remission after transplantation was 29 months. The following factors were predictive for longer survival and freedom of progression in a univariate analysis: Male sex, age less than 45 years, a low serum-beta-2-microglobulin value at diagnosis, prior administration of only one treatment regimen, response on conventional chemotherapy immediately pretransplant and the use of a preparative regimen including melphalan. The last factor, in addition to stage I disease at diagnosis, male sex and responsive disease immediately pretransplant, were also demonstrated as independent predictive variables for longer survival in a multivariate analysis. Progression-free survival was significantly better for patients who were in complete remission after transplantation, as compared to those with persisting signs of disease. We conclude that high-dose chemo-radiotherapy with autologous stem cell transplantation can induce long-term responses, primarily in younger, male patients with chemotherapy-responsive early disease. High-dose melphalan, as single drug or in combination, appeared to be superior to other regimens. The chance of being persistently disease-free seemed to be greatest for patients being in complete remission already before the transplantation.