Cardiovascular actions of S. miltiorrhiza (SM) were studied on systemic blood pressure in the rat. Langendorff cardiac preparation in the guinea pig, and four types of vasculature in the dog, including coronary, renal, femoral, and mesenteric arteries. SM induced dose-related hypotension without changing heart rate. The hypotension was antagonized by atropine, propranolol, and chlorpheniramine plus cimetidine. In the isolated whole-heart preparation, SM increased coronary blood flow significantly for 15 min and positive inotropic action for 3 min after pulse injection. SM relaxed all arteries at low concentration (3.0 mg/ml) and contracted all but the coronary artery at higher concentration (10.0 mg/ml). The coronary artery relaxed at all doses of SM tested.