Abstract: To clarify whether a brief period of angiotensin converting enzyme inhibitor,captopril, treatment during the developmental phase of hypertension in young spontaneously hypertensive rats （SHR） could alter the natural history of hypertension development, twelve 4-week-old SHRs were randomized into a captopril （n = 6 ） and a control （n = 6 ） group. Captopril （60 mg/kg·d） was given from the age of 4 to 7 weeks,and then the drug was discontinued. Systolic blood pressure （BP） measured by indirect tail-cuff technique was determined weekly from 8 to 15 weeks. At the age of 16 weeks, intra-carotid artery BP was measured, and heart weight and plasma angiotensin Ⅱ level determined. The results showed that a 3-week period of captopril treatment in young SHP could postpone the development of hypertension.