The aim of the present study was to evaluate pulmonary function tests and arterial oxygen transport in patients with pulmonary hypertension due to congestive heart failure before and after cilazapril treatment. Thirty patients (16 men and 14 women, mean age, 65 18 years) with congestive heart failure and 30 healthy volunteers (20 men and 10 women, mean age 59 +/- 12 years, p > 0.05) were included in the study. All patients underwent evaluation of pulmonary function by spirometry and arterial blood gas analysis. Arterial oxygen saturation and arterial oxygen transport changed significantly after treatment (81 +/- 7 to 87 +/- 8 and 317 +/- 74 to 392 +/- 8, respectively). Forced expiration volume in 1 second, vital capacity and total lung capacity were increased after cilazapril treatment (2.55 +/- 0.7 to 2.61 +/- 0.8, 3.2 +/- 0.9 to 3.3 +/- 1.0 and 3.6 +/- 0.9 to 4.1 +/- 1.1, respectively p < 0.05). In conclusion, short-term cilazapril administration improved pulmonary function and arterial oxygen transport because it increased cardiac output, produced pulmonary vasodilatation, improved the pulmonary hemodynamics and removed interstitial fluid