Four patients on regular dialysis treatment whose blood pressure was well controlled, developed malignant hypertension while receiving maintenance recombinant human erythropoietin (r-Hu-EPO). None of these patients had a haematocrit greater than 35% at any stage, and clinically, none had any evidence of fluid overload. Initially, they were all managed by stopping r-Hu-EPO and intensification of antihypertensive therapy. However, none of the patients responded, and venesection of 500 ml of blood was performed in each case with swift and sustained response.