Because of progress in supportive therapies, the upper limit of age for conventional allogenic stem cell transplantation (allo-SCT) is rising. We retrospectively evaluated the impact of age on transplant outcomes in patients older than 50 years of age who underwent conventional allo-SCT in 8 institutions in Japan. The median age was 52-years old (range 50 to 65). The underlying diseases included severe aplastic anemia (n = 3), acute myelogenous leukemia (n = 20), acute lymphoblastic leukemia (n = 10), chronic myelogenous leukemia (n = 11), myelodysplastic syndrome (n = 18), and non-Hodgkin lymphoma (n = 3). Forty two patients (67%) with hematological malignancies received allo-SCT in an advanced disease stage at the time of transplant. The two-year overall survival and disease-free survival rate were 50.1% and 43.6%, respectively. In patients with hematological malignancies, the two-year probability rates of survival were 54.3% with standard risk patients, and 45.9% with poor risk patients. The severity of acute GVHD, the kind of grafts, and age (> or = 55) were related to poor prognosis. Our data suggest that prophylaxis of acute GVHD and selection of the graft is more important for older patients, and that patients less than 55-years old can be candidates for conventional allo-SCT.