In heart failure, the benefits of adding angiotensin-receptor blockade to ACE inhibitors have been studied only with submaximal doses of ACE inhibitors. We included 20 patients (LVEF 24 7%, NYHA II-III), with no clinical or therapeutic variations in the previous three months, who were receiving maximal doses of ACE inhibitors. We added losartan 50 mg once a day. At six months, SBP decreased (115 8 vs. 106 9 mmHg; p = 0.001), LVEF increased (24.4 7 vs. 34.1 7%; p < 0.001), ventricular end-diastolic volumes decreased (220 58 vs 190 46 ml; p = 0.007), and SPAP decreased (43 8 vs. 35 7 mmHg; p < 0.001). Seven patients improved one degree on the NYHA scale (p = 0.004), but VO2max did not change (20.8 5.2 vs. 21.8 5.0 ml/kg/min, p = 0.120). Plasma levels of norepinephrine, at rest and maximal exercise, brain natriuretic peptide, and renin were similar. After maximum ACE inhibitor doses, the addition of losartan is safe and associated with an improvement in ventricular function and NYHA functional class, but with no change in neurohormonal status.