Background and Objectives : Pulmonary hypertension is a life threatening disease characterized by progressive pulmonary hypertension and may ultimately results in right heart failure and death. Currently available treatment are diverse, but these therapies alone can not reverse the disease process, although they have a beneficial clinical effect. This study was designed to investigate the combination therapy of simvastatin and sildenafil in monocrotaline (MCT)���induced pulmonary hypertension in rats. Materials and Methods : Fourty 8-weeks-old rats were randomized to control, MCT (60 mg/kg, sc), MCT with simvastatin (2 mg/kg/day, po), MCT with sildenafil (25 mg/kg/day, po) and MCT with simvastatin plus sildenafil groups. Three weeks later, systolic right ventricular pressure (RVP), right ventricular hypertrophy (RVH, RV/LV+septum), medial wall thickness (MWT) of pulmonary arterioles were measured. Immunohistochemical stain for PCNA, TUNEL and Western blot for eNOS were done. Results : RVP was significantly increased in MCT group compared with that of the controls (51.5짹1.5 vs. 22.2짹0.7 mmHg, p<0.05), which was markedly suppressed in the simvastatin, sildenafil and their combination group (32.4짹1.2, 31.4짹1.0 and 33.4짹0.7 mmHg, p<0.05). RV/LV+septum ratio (0.32짹0.02, 0.34짹0.02 and 0.29짹0.01 vs. 0.45짹0.03) and MWT (0.2짹0.01, 0.19짹0.03 and 0.18짹0.01 vs. 0.34짹0.02) were also attenuated with treatment. The increased expression of PCNA in MCT group was also depressed in treatment group. The decreased expression of eNOS in MCT group was normalized in treatment group. But the combination therapy was not additive effect than monotherapy. Conclusion : These results suggest that simvastatin and sildenafil attenuates the MCT-induced pulmonary hypertension. But the combination of simvastatin and sildenafil were not superior than monotherapy.