Objective To investigative the effects of combination treatment with simvastatin and aspirin in a rat model of monocrotaline-induced pulmonary hypertension. Methods Sixty male Sprague-Dawley rats were randomly divided into a control group, a simvastatin group, an aspirin group, and a combination treatment group. The control group received monocrotaline injection subcutaneously to induce pulmonary hypertension. Simvastatin ( 2 mg/kg) , aspirin ( 1 mg/kg) , or simvastatin ( 2 mg/kg) + aspirin ( 1 mg/kg) was administered once daily to the rats of treatment groups respectively for 28 days after monocrotaline injection. Mean pulmonary arterial pressure ( mPAP) was detected by right heart catheter.Right ventricular hypertrophy index ( RVHI) was calculated as the right ventricle to the left ventricle plus septum weight. Histopathology changes of small intrapulmonary arteries were evaluated via image analysissystem. Interleukin-6 ( IL-6) level in lung tissue was determined by ELISA.Results Compared with the control group, simvastatin or aspirin decreased mPAP [ ( 34. 1 ±8. 4) mm Hg, ( 38. 3 ±7. 1) mmHg vs.( 48. 4 ±7. 8) mmHg] and increased arterial wall diameter significantly ( P lt; 0. 05) . The combination treatment group showed more significant improvement in mPAP, RVHI and pulmonary arterial remodeling compared with each monotherapy ( P lt;0. 05) . Moreover, the combination therapy had additive effects on the increases in lung IL-6 levels and the perivascular inflammation score. Conclusions Combination therapy with simvastatin and aspirin is superior in preventing the development of pulmonary hypertension. The additive effect of combination therapy is suggested to be ascribed to anti-inflammation effects.