It has been speculated that testosterone stimulates erythropoiesis. We hypothesized that hemoglobin levels in hemodialysis (HD) patients are associated with serum testosterone concentrations. Testosterone, hemoglobin, and other biochemical parameters were measured in a representative sample of 98 chronic HD patients (50 male, 48 female; age 30-90 years, mean 65±13.9 years). We investigated relations among serum testosterone concentration, hemoglobin, ferritin, albumin, body mass index, lean body mass, total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol, triglycerides, high-sensitivity C-reactive protein (hsCRP), calcium (Ca), P, intact parathyroid hormone, N-terminal pro-brain natriuretic peptide, Karnofsky performance status, and blood pressure (BP) before and after HD. A statistically significant positive correlation between testosterone and hemoglobin was found in all patients (r=0.25, P<0.01), men (r=0.34, P<0.02), but not in women (r=0.27, P=0.07). Multiple regression analysis for all patients has shown statistically significant association between hemoglobin and testosterone (P<0.001), hsCRP (P<0.005), lean body mass (P<0.05), post-HD systolic (P<0.04), and diastolic BP (P<0.005). Multiple regression analysis in men has shown an association between hemoglobin and testosterone (P<0.04) and post-HD diastolic BP (P<0.04) and in women association between hemoglobin and testosterone (P<0.04), Ca (P<0.03), and post-HD diastolic BP (P<0.03). We found an association between serum testosterone concentration and hemoglobin in male and female HD patients.