The effects of long-term treatments with 7 antihypertensive agents on the functions of endothelium-dependent relaxation were studied in spontaneously hypertensive rats (SHR). It was found that captopril, atenolol and dihydrochlorothiazide (DHT) could prevent the endothelium in SHR from impairing, but tetrandrine, nitrendipine, prazosin and dihydralazine could not. The improvement of the function of endothelium-dependent relaxation was not related to the blood pressure lowing.