To detect changes in vascular physiology associated with early atherosclerosis, we studied whether alterations in coronary flow reserve, as assessed by positron emission tomography imaging with intravenous dipyridamole, would be related to risk factor variables in healthy young men. The number of conventional risk variables correlated significantly with coronary flow reserve (r = -0.58, p = 0.0007), suggesting that alterations in functional vascular reactivity are related to the cardiovascular risk status already in healthy young men.