Recombinant human erythropoietin is increasingly used to treat anemia in predialysis patients. Approximately 33-40% of patients ultimately receiving dialysis or a transplant may be eligible for treatment, thus increasing the costs. Clinical trials demonstrate no significant alteration in the progression of renal disease, secondary to changes in systemic hemodynamics or blood volume, provided that blood pressure is controlled. Hypertension results from changes in viscosity and erythrocyte fluidity, loss of hypoxic vasodilatation, and changes in blood volume. The predialysis patient treated with recombinant human erythropoietin is likely to need aggressive antihypertensive therapy and vigorous diuresis. Cardiac output remains unchanged in the absence of blood volume expansion. The effects on left ventricular hypertrophy, left ventricular volume, or exercise-induced ischemic electrocardiographic changes in predialysis have not been studied systematically. Doses of recombinant human erythropoietin in predialysis patients tend to be lower when administered subcutaneously rather than intravenously, but the comparative cost-effectiveness of different dosing strategies is currently unknown. The dosing frequency can vary from three times a week to twice a month. The effect of anemia correction on the 'rehabilitation' of predialysis patients remains to be addressed.