Previous epidemiological studies have suggested that uric acid is an independent risk factor for incident hypertension, whereas few studies have evaluated the effect of hyperuricemia on blood pressure control in hypertensive patients. We investigated whether hyperuricemia predicts uncontrolled hypertension through a large-scale prospective cohort study with hypertensive patients treated with fimasartan in the Republic of Korea (the Kanarb-Metabolic Syndrome study).Of the 10,601 hypertensive patients who were recruited from 582 private clinics and 11 university hospitals at baseline, 7725 completed the follow-up after 3 months of fimasartan medication, and 6506 were included in the analysis after excluding those with missing values. We estimated the risk of uncontrolled hypertension after 3 months (>/=130/80 mm Hg in those with diabetes or chronic renal failure and >/=140/90 mm Hg in the remaining patients) related with baseline hyperuricemia (serum uric acid >/=7 mg/dL in males >/=6 mg/dL in females) using multiple logistic regression models.Hyperuricemia increased the risk of uncontrolled hypertension after 3 months of fimasartan medication (odds ratio, 1.247: 95% confidence interval, 1.063-1.462). Males in the highest quartile of uric acid level were at a 1.322 (95% confidence interval, 1.053-1.660) times higher risk of uncontrolled hypertension in reference to the lowest quartile: the same analyses in females were not significant. Patients without metabolic syndrome had significantly higher odds of uncontrolled hypertension with hyperuricemia (odds ratio, 1.328: 95% confidence interval, 1.007-1.751).Hyperuricemia predicted uncontrolled hypertension even after 3 months of fimasartan treatment in hypertensive patients.