Objective: We aimed to investigate the relation between the presence of fragmented QRS (FQRS) and exercise intolerance as assessed by 6 minute walking test (6MWT) and its association with coronary flow reserve (CFR). Methods: One hundred and twenty patients with hypertension (age: 47.3 þ 6.9) who were never treated and without left ventricular hypertrophy underwent 6MWT. Echocardiographic examin- ation was obtained for all patients. CFR was calculated as the hyperemic to baseline mean vel- ocity ratio (hyperemia was induced by intravenous adenosine 0.14mg/kg/min). Patients were stratified into one group with FQRS and another group without FQRS. Forty-eight normotensive subjects with a mean age of 45.7 þ 5.3 were recruited and served as a control group. Results: The frequency of FQRS was 49% in hypertensive patients versus 2% in control subjects. Patients with FQRS had higher systolic blood pressure (p < .05; <.01), a significant lower 6MWTD (p<.001), increased LAVI (p<.05), increased E/e’ ratio (p<.01) and lower CFR (p<.001) com- pared with those without FQRS and controls. FQRS was inversely correlated with CFR (0.531; p < .001) and 6 MWTD (0.415; p < .001) and positively correlated with E/e’ (0.352, p < .02) and LAVI (0.296; p<.05). By a multivariate regression analysis, FQRS (OR1⁄46.13; p<.001) and CFR (OR 1⁄4 3.28; p < .001) were the only two independent predictors for decreased 6 MWTD in hyper- tensive patients. Importantly the !3 cutoff number of leads was found to be the best predictor of CFR < 2.0 in hypertensive patients. Conclusion: FQRS is frequent and an independent predictor of reduced exercise tolerance in hypertensive patients. More so, it is significantly associated with decreased CFR and left ven- tricular diastolic dysfunction. In light of these findings, fragmented QRS might be considered a simple marker for risk stratification of hypertensive patients.