Purpose: to assess the early hemodynamic changes after elective mitral valve replacement (MVR) in patients with severe and mild pulmonary arterial hypertension (PAH). Methods: a total of 45 consecutive patients, who were candidate for elective MVR, were enrolled in this prospective observational study. Patients were divided into two groups based on the absence (group A, 20 patients) or presence (group B, 25 patients) of severe pulmonary artery hypertension (PAH) defined as systolic pulmonary artery pressure ≥50 mmHg measuring by catheterization. MVR was performed using standard cardiopulmonary bypass (CBD) technique. The hemodynamic and arterial blood gas assessments were carried out at baseline before the induction of general anesthesia, in the operating room immediately after MVR, and then continued after stabilization of hemodynamic status with 2 hr interval up to 24 hours. Results: The mean CPB and aortic cross-clamp times were similar in two groups (95.3 ± 49.5 and 61.8 ± 36.3 minutes in group A and 103.1 ± 34.7and 61.9 ± 20.0 minutes in group B). In group A, the mean PAP showed an increase immediately after the operation (from 40.4 ± 7.3 to 43.10 ± 6.2 mmHg) and then decreased significantly to 32.5 ± 3.9 mmHg (P <0.05). In group B, the mean PAP showed no significant reduction immediately after MVR, but it decreased significantly below the range of severe PAP over the first 24 hours. Conclusion: MVR is safe and effective even in patients with severe PAH. The anesthetic technique and postoperative cares can be useful in improving the outcome in such patients.