We investigated whether the presence of diabetes mellitus (DM) was related to the severity of the anemia observed in patients with renal failure who were not receiving dialysis. Forty patients were examined, (19 with long-term type II DM (DM-CRF), 21 with renal failure due to other causes (non-DM-CRF)). The two groups did not differ significantly as to age, sex, serum creatinine or erythropoietin. Hemoglobin was significantly (p < 0.005) lower in the DM-CRF patients (9.5 +/- 2.1 g/dl) than in the non-DM-CRF patients (11.2 +/- 2.0 g/dl). Multiple regression analysis indicated that higher serum creatinine levels and the presence of DM were independent risk factors for anemia (R2 = 0.494, p < 0.001). DM appeared to be a risk factor for the severity of anemia in patients with renal failure who were not receiving dialysis.