Seven anaemic patients with predialysis chronic renal failure were treated with human recombinant erythropoietin. Anaemia was improved, with a 31% increase in haematocrit, but blood pressure increased in all patients with an average of 12% in systolic (P less than 0.01), 14% in diastolic (P less than 0.05) and 13% in mean blood pressure (P less than 0.05). Blood volume was significantly increased by an average of 12%. Cardiac output increased in three of seven patients, and total peripheral resistance in four. GFR, RBF and RPF were not changed but filtration fraction increased significantly (P less than 0.05). It is suggested that blood pressure elevation might be developed as a result of volume expansion, elevated cardiac output, and increased total peripheral resistance.