We statistically analyzed the hematologic findings of patients with refractory anemia (RA) to identify parameters associated with a poor prognosis. We first separated the RA patients into two groups: one group with disease progression and one without. The patients with disease progression were predominantly male and had a significantly higher percentage of bone marrow (BM) blasts at the time of diagnosis (3.06 +/- 1.29% vs. 1.44 +/- 1.38%, P < 0.005). This finding was confirmed when the patients were separated into the two groups; those who survived and those who expired (BM blasts: 2.68 +/- 1.59% vs. 1.37 +/- 1.27%, P < 0.005). The survival probabilities were calculated depending on whether or not the RA patients had > or = 3% BM blasts. The RA patients with > or = 3% BM blasts had a significantly worse prognosis (P < 0.01) than the patients with < 3% BM blasts. Notably, the RA patients with > or = 3% BM blasts did not show any significant differences in the incidence of disease progression, mortality rate, or survival probability, when compared with the patients with RA with an excess of blasts (RAEB). The present findings indicate that RA patients are heterogeneous with regard to prognosis, and the RA patients with > or = 3% BM blasts might have a poorer prognosis than those with fewer BM blasts. Thus we propose a general approach in predicting the prognosis of RA patients: those with complex chromosomal changes will expire shortly. Secondly, when the patients do not have any complex changes, the prognosis might be linked to the percentage of BM-blasts at the MDS diagnosis.