Autologous hematopoietic stem cell transplantation was used for treatment of 384 patients with multiple myeloma in 37 centers during the years 1986-1994. An analysis of prognostic factors was performed in 207 of these patients. One hundred forty one were males and 66 females, and median age was 49 years (range, 24-68). Actuarial survival at 78 months is 45%. Factors associated with a good prognosis were: response on chemotherapy immediately pretransplant, administration of only one treatment regimen, a low serum-beta 2-Microglobulin value at diagnosis and the use of a conditioning regimen including melphalan. In a multivariate analysis, response status pretransplant, age < 45 years, melphalan conditioning and non-TBI conditioning were independently predictive for longer survival, while transplantation after only one line of primary treatment and isotype other than light-chain were of borderline significance. Post-transplant alpha-interferon treatment was associated with improved survival in responsive patients. Eighteen patients treated in one center (Huddinge) passed a double autograft program, and 14 are in continuous complete remission ([CR]; n = 10) or good partial remission (n = 4) at a median time of 17 months after the first transplant (range, 2-38). In five CR patients, polymerase chain reaction (PCR)-analysis of the clone-specific immunoglobulin-rearrangement was performed, and four are PCR-negative up to 33+ months after the first transplantation. We conclude that autografting in myeloma is most effective when applied early in the course of disease in younger, chemotherapy-reponsive patients. Alpha-interferon maintaince treatment seems to be beneficial with respect to improved survival.(ABSTRACT TRUNCATED AT 250 WORDS)