The projected outcome of allogeneic BMT for myeloma based on the EBMT data is as follows: for patients transplanted after first line therapy there is a 30% risk of transplant related death, a 55% chance of being alive at 5 years and a 35% chance of being alive in complete remission at 5 years. If BMT is performed later in the course of the disease, the risk of transplant related death is increased and the chance of long term relapse-free survival correspondingly reduced. Conversely, ABMT has a low mortality risk, but there is currently no evidence that ABMT using unpurged marrow can produce long term cure as no series has shown any evidence of a plateau in remission duration. The early results of maintenance interferon are encouraging but longer follow-up is needed to determine whether the proportion of patients in continuing remission at 5 years will approach that seen after allogeneic BMT. Early results of peripheral blood stem cell transplantation are also encouraging but longer follow-up is required. It remains extremely important when comparing results of ABMT with chemotherapy alone to compare similar patient groups, bearing in mind that patients who have autologous transplantation in first response are by definition responders with good performance status and without significant renal failure. In order to address this problem in a prospective manner, a randomised study has been planned by the EORTC in collaboration with the EBMT. In this study, patients with adequate renal function will be randomised at diagnosis to chemotherapy followed by either autologous BMT or continuing chemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)