Background: Hypertensive response to exercise (HRE, defined as systolic BP > 210mmHg in men and systolic BP > 190mmHg in women) may be related to excess stimulation of the sympathetic nervous system and the renin-angiotensin-aldosterone system during exercise and has been reported to be associated with adverse cardiovascular prognosis. Insulin resistance is associated with increased sympathetic activity and elevated angiotensin II which may contribute to the excessive increase in arterial blood pressure during exercise. In this study, we hypothesized that increased insulin resistance will be significantly associated with hypertensive response to exercise in non-diabetic, well controlled hypertensive patients. Methods: Two hundred seventy five hypertensive patients were included in this study and standard Bruce protocols were used for symptom-limited treadmill test. HOMA IR index using serum fasting glucose and insulin was calculated for insulin resistance. Results: There were 79 patients with hypertensive response (age 56.1짹9.4 years, N=79) and 196 patients without hypertensive response (age 53.9짹8.9 years, N=196). Baseline characteristics were similar in both groups. Insulin resistance, assessed by HOMA index, was significantly higher in hypertensive response group as compared to control (HOMA=2.63 짹 1.57 vs 1.77 짹 0.88, P-value < 0.001). HOMA was an independent predictor of HRE when controlled for age, sex, BMI and baseline SBP [OR=1.96(1.45-2.66), P-value < 0.001]. Also, HOMA was significantly correlated with the degree of peak SBP elevation controlled for age, sex, BMI and baseline SBP as well (棺=0.302, P-value < 0.001). Conclusions: Insulin resistance is a significant determinant of hypertensive response to exercise. Further studies to determine the prognostic significance of this finding is warranted. This work was supported by a grant of Ministry of Health and Welfare, Republic of Korea (00-PJ6-PG5-23-0001)