Abstract: The two-way effects of dl-tetrahydropalmatine (THP) on cardiac hemodynamics were examined in 8 anesthetized open-chest dogs. Intravenous injection of THP (5 or 15 mg/kg) produced a dose-dependent positive inotropic effect rapidly. The left ventricular systolic pressure (LVSP), maximal rate of change of intraventricular pressure (dp/dt_max) and cardiac index (CI) were increased significantly, then decreased rapidly. Systolic blood pressure (SBP), diastolic blood pressure (DBP), V_CE at dp/dt_max (V_CE-dp/dt_max) and total peripheral resistance (TPR) were decreased. The time constant of isovolumic diastolic pressure decay (T_value) was increased after drug administration. When marked depression of cardiac contractility appeared after drug administration, CI decreased slightly.