Objective: To study the effects of hypertension and aging on structure and function of coronary vasculature. Methods: Spontaneously hypertensive rats(SHR) and normotensive Wistar-Kyoto rats(WKY) strains at 4,16,26,40, and 55 weeks of age were studied. Maximal coronary flow(MCF) was measured using an isolated perfused rat heart model. Outer dimeter(OD), lumen dimeter(LD), cross-sectional area(CSA), and CSA/LD were analysed by computer. Results: LD demonstrated a significant hypertension related decline and was not effected by aging. CSA and CSA/LD in arterioles<100 μm demonstrated a significant hypertension-related increase and was not effected by aging. There was a significant hypertension- and age-related increase in CSA and CSA/LD in arterioles>100 μm. In addition, there was a significant hypertension- and age-related decline in MCF. The tight linear relation between CSA/LD in arterioles>100 μm and MCF. Conclusion: Both hypertension and aging are accompanied by structural and functional alterations of the cornoary vasculature. Structural alterations in arterioles>100 μm may be the main reason for MCF decrease.