A five-agent GVHD prophylaxis programme consisting of cyclosporin A, methotrexate, anti-thymocyte-globulin, pentaglobin and metronidazol was given to 48 recipients of unrelated donor marrow with chronic myelogenous leukemia, acute leukemia, myelodysplastic syndromes, and familiar lymphocytic hemophagocytosis of an average age of 33.5 (0.6-56) years. GVHD grades II-IV occurred in 18 patients (39%) and grades III-IV in five patients (11%). Chronic GVHD developed in nine patients (23%), three limited and six extensive. Fifteen patients died. Clinical relapse was detected in eight patients. Four patients died as a consequence of the underlying disease and subsequent treatment, 11 patients died of transplant-related causes. After a median follow-up of 19 months, the overall and disease-free survival are 67% and 62%, respectively. Survival by age is as follows: 0-19 years: 12/13 patients; 20-39 years: 14/25 patients; 40-59 years: 7/10 patients. The five-agent GVHD prophylaxis regimen is effective. Matched-unrelated donor transplants can be carried out safely in patients younger than 50 years of age. The results in patients younger than 20 years of age should encourage matched-unrelated donor transplants at earlier stages of the disease.