Body fluids, particularly in the thorax, are increased in moderate congestive heart failure, even if diuretic treatment is appropriate. Ultrafiltration, differently from diuretics, removes isotonic fluid and therefore the greatest possible amount of sodium per unit of fluid withdrawn, providing a physiologic dehydration. This results in improvement in the patient's clinical condition, exercise capacity, lung function, as shown by improvement of standard pulmonary function tests, lung mechanics during exercise, and norepinephrine kinetics during exercise and orthostatic tilting. Copyright (C) 2002 S. Karger AG, Basel.