BACKGROUND AND OBJECTIVES: The diagnostic and prognostic importance of exaggerated blood pressure response to exercise is controversial. Endothelial dysfunction has been demonstrated in patients with atherosclerosis and risk factors for coronary artery disease, but there is a lack of information in patients with exercise hypertension. Thus, we designed this study to evaluate the endothelial function in patients with exaggerated blood pressure response during exercise. SUBJECTS AND METHODS: Exercise hypertension is defined as a systolic blood pressure >or= 210 mmHg in men, and >or=190 mmHg in female, during Treadmill tests. Using a high resolution ultrasound technique, the endothelial function of the brachial artery, in patients with exercise hypertension (n=25), and control subjects (n=25), were investigated. RESULTS: Endothelial-dependent vasodilation were impaired in patients with exercise hypertension (7.77+/-5.14 vs. 2.81+/-2.29%, p<0.05). On univariate analysis, the extent of vasodilation was significantly correlated with age (r=0.43, p<0.05) and systolic blood pressure (r=0.39, p<0.05). CONCLUSION: We conclude that patients with exercise hypertension have impaired endothelium-dependent vasodilation. Exercise hypertension is a finding, which may, by itself, raise concern when interpreted as an exercise test. This study also supports the concept that endothelial dysfunction may play a role in exercise hypertension.