Background: Pulmonary artery hypertension is a disorder with limited treatment options and poor prognosis. We studied the effect of tadalafil, a selective phosphodiesterase type 5 inhibitor, in patients with this disease.Patients and Methods: In fifty patients subjected to valve surgery (26 males, 24 females) aged 19–40 years, with pulmonary artery hypertension, 10 mg tadalafil single dose was given to 25 patients after induction of anesthesia , and its effect was compared to a placebo given to the other 25 patients, all fifty patients had a comprehensive Transoesophageal echo examination including tissue Doppler and Tei index .Results: Tadalafil resulted in a marked improvement in right ventricular function as regards tissue Doppler and Tei index (0.31±0.05) compared to (0.34±0.02) in control group (p value =0.01) and pulmonary artery pressure(52.6±12.17) compared to control group(59.60±11.31) (p value =0.04).Conclusion: 10 mg Single dose tadalafil was well tolerated and had a beneficial effect in patients with pulmonary artery hypertension undergoing valve surgery.