Seventeen patients received marrow transplants from their HLA-matched, MLC-negative, sibling donors. Nine patients had progressive disease not responding to conventional treatments, while the other 8 patients were rated as responders. The most frequently used conditioning regimen consisted of total body irradiation and high-dose multi-agent chemotherapy with cyclophosphamide plus either oral melphalan (5 cases) or BCNU (1 case) on both these drugs (7 cases). Twelve patients were valuable for response to BTM: 7 of them (6 responders and 1 with advanced refractory MM) entered complete remission, while 5 had sustained decrease in tumor mass that ranged between 72% and 93%. Eleven patients died of transplant-related causes, 1 of them with signs of progressive disease. The remaining 6 patients are alive and 5 of them maintain a complete remission status 4 to 67 (median 36) months after BMT.