Both hyperuricemia and echocardiographically determined left ventricular (LV) mass have a well-determined association with cardiovascular morbidity and mortality. However, whether or not there is a sex difference in the association of serum uric acid level with LV mass has never been systematically explored. We examined the sex-specific relation of serum uric acid level and echocardiographic indexes of LV structure in never-treated patients with essential hypertension. We enrolled 160 never-treated hypertensive patients (89 men and 71 women) to assess the possible relationship between LV mass and serum uric acid levels. LV measurements were performed according to the recommendations of the American Society of Echocardiography and the Penn Convention. LV mass was indexed by height, body surface area and height raised to the 2.7th power. A positive significant correlation between LV geometry (LV mass, indexed LV mass and relative wall thickness) and serum uric acid level was found in male hypertensive patients but not in female hypertensive patients. Independent determinants of serum uric acid levels in male hypertensive patients were LV mass and serum creatinine levels. In addition, male hypertensive patients with concentric hypertrophy showed the highest serum uric acid levels. In comparison, independent determinants of serum uric acid levels in female hypertensive patients were age and serum creatinine levels. In conclusion, these findings indicate a sex difference in the association of uric acid with LV geometry in Japanese hypertensive patients. In addition, the finding that the highest levels of serum uric acid were observed in our male hypertensive patients with concentric hypertrophy confirmed the previous reports that these patients have the highest risk for cardiovascular morbidity and mortality.