A P113 Saralasin infusion test was performed in 10 patients on long-term regular hemodialysis. Six patients were considered to have hypertension resistant to dialysis treatment and 4 had their arterial pressure controlled by dialysis. 2. Five out of 6 resistant and 3 out of 4 responsive patients had a positive response to Saralasin associated with a normalization of diastolic arterial pressure. 3. The value of the Saralasin infusion test to pre-select the patients for bilateral nephrectomy is discussed and it is felt that a negative test may be of more value in encouraging more aggressive ultrafiltration in hypertension apparently resistant to dialysis therapy.