For patients younger than 60 years with multiple myeloma in a stage requiring chemotherapy high dose chemotherapy followed by autologous blood stem cell transplantation appears to be the best therapeutic option. Conditioning regimens resulting in a high proportion of patients with 90% tumor reduction (very good partial or complete remissions) should be preferred. A good quality of remission is a prerequisite for prolonging the disease free survival. World-wide the tandem high dose melphalan protocol developed by Barlogie and coworkers is deemed the most effective conditioning regimen. A pilot study in our clinic with an intensified high dose regimen combining idarubicin, melphalan and cyclophosphamide showed similar remission rates. The application of peripheral blood stem cells reduces the treatment related mortality to less than 10%. It is expected that more than 50% of patients treated with high dose chemotherapy and autologous peripheral blood stem cell transplantation will survive at least 5 years. Therefore, the prognosis of such patients is significantly improved compared with patients treated with conventional chemotherapy. Treatment related mortality after allogeneic blood stem cell transplantation is about 40%. Therefore, during the first 2 to 3 years after transplantation the prognosis of patients after allogeneic transplantation is inferior to that of patients receiving autologous transplants. Subsequently, patients with allogeneic transplants do better, because the relapse rate after allogeneic transplantation is decreased and some patients may achieve long term remissions or even cures. Therefore, we recommend allogneic blood stem cell transplantation for patients younger than 50 years if an HLA-identical sibling donor is available and there are no contraindications. For patients older than 60 years the Alexanian protocol is still the therapeutic standard. On the other hand, successful application of high dose chemotherapy and autologous blood stem cell transplantation in patients of this age group has been reported. Therefore, clinical trials are required to clarify whether the prognosis of patients older than 60 years can be improved with treatment strategies including high dose chemotherapy.