Seventy-five cases of myelodysplastic syndromes (MDS) in the aged (over 60 years) were analysed for hematological findings, immunological parameters and response to treatment in respect to prognostic significance. They were diagnosed according to the FAB classification, but patients with hypoplastic marrow were included if myelodysplasia was evident. Thirty-four percent of patients with primary acquired refractory anemia (PARA) or primary acquired sideroblastic anemia (PASA), and 36% of patients with RA with excess of blasts (RAEB) had hypoplastic bone marrow. The positive rates of antinuclear antibody in PARA or PASA, and of rheumatoid factor in PARA or PASA and in RAEB were higher than those in normal aged controls. Cellularity of bone marrow was inversely related to the length of survival. Among the patients with PARA or PASA, survival time was significantly longer in the group of hypoplastic bone marrow than in the group of hyper- or normo-plastic bone marrow, and in the group of good responder to treatment than in the group of poor responder and nontreated patients.