We examined whether impaired coronary flow reserve in healthy men is associated with changes in cardiac performance and exercise-induced ischemia. A comparison between 7 asymptomatic men with low flow reserve (<3.5) and 8 men with normal flow reserve (>3.5) showed no differences in these parameters, suggesting that the mechanisms that control myocardial blood flow during exercise remain normal despite the alterations in the mechanisms that control the vasodilatory reaction to dipyridamole.