Aim To observe the effects of angiotensin Ⅱ 1 receptor antagonist Losartan on coronary and systemic hemodynamics in the normotensive and renovascular hypertension rats. Methods Coronary blood flow (CBF) intra-arterial blood pressure, heart rate, and coronary vascular resistance (CVR) were measured at rest, during isometric exercise before and 60 min after Losartan (25 mg/kg, ig). Results The drug induced a prompt, significant decrease in mean arterial pressure (MAP) and a sustained increase in CBF, but no effects to normotensive rats. Conclusions These observations suggest that angiotensin Ⅱ maintains the ability to alter the control mechanisms of CBF even under long-term conditions and that Losartan reverses the angiotensin Ⅱ-induced effects on coronary hemodynamic.