Abstract: The effects of praeruptorin C (Pra-C) on cardiac dysfunction, myocardial compliance, and collagen content in renovascular hypertensive rats have been studied. In rats with left ventricular hypertrophy (LVH), the ratio of cardiac flow (CF)/heart wet weight (HWW) and cardiac output (CO)/HWW decreased by 20.1% and 35.5%; LVSP and -dp/dt_max decreased by 19.4% and 42.1%, while LVEDP and T value were increased by 186.4% and 226%.The left ventricular diastolic pressurevolume (P-V) curve was shifted to the left and down ward compared with that of shamoperated rats. The hydroxyproline content was 5.93±0.82 mg·g^-1 dry weight in the left ventricular myocardial tissue of rats with LVH which was higher than that of shamoperated rats(eg. 4.01±0.47 mg·g^-1). The content did not change in the right ventricular myocardium. After treated with PraC for nine weeks, the CF/HWW and CO/HWW increased by 31.3% and 25.1%, the LVSP and -dp/dt_max increased by 16.7% and 27.8%. The LVEDP and T value was reduced by 34.9% and 36.5%, respectively, compared with those of LVH. The P-V curves of these rats were shifted to the right and in the up-ward direction.　The hydroxyproline content was 4.52±0.3 mg·g^-1 dry weight in the left ventricular tissue. These results indicate that Pra-C improved the cardiac contractility and relaxation by increasing the coronary flow and cardic output, and decreasing the collagen content in the ventricular myocardium.