Separate ultrafiltration followed by haemodialysis (U.F.-H.D.) using Gambro Major or Cordis-Dow hollow-fiber dialyzers were evaluated in 10 dialysis patients over a mean period of 4 1/2 months and 455 U.F.-H.D. procedures. Fluid control was facilitated in oedematous patients but the number of hypotensive episodes during the combined procedure requiring intravenous 5% saline did not significantly decrease. No significant improvement in hypertension was noted. Ultrafiltration (U.F.) alone for acutely water overloaded, azotaemic patients proved very useful. Two to five liters of oedema fluid could be removed asymptomatically in one to three hours using transmembrane pressures of 250 to 500 mmHg and U.F. rates of 10 to 42 ml/min. Two patients became acutely and symptomatically hypotensive. One was an insulin dependent diabetic in whom 3800 ml were removed in 75 minutes and the other a hypertensive patient undergoing treatment with Minoxidil and propranolol.