Determinants and risks associated with serum uric acid were investigated in 822 elderly hypertensive patients treated with hydrochlorothiazide and triamterene or placebo. Pretreatment serum uric acid levels were significantly higher in men than in women and had positive correlation with serum creatinine. After adjustment for serum creatinine, positive correlations of serum uric acid with body weight and fasting blood glucose in women and with serum cholesterol in men were significant. During follow-up, serum uric acid increased significantly in the treated patients, but remained unchanged in the placebo group. Total, cardiovascular, and noncardiovascular mortality were unrelated to initial serum uric acid levels. One placebo patient and seven treated patients developed gout. Of those seven, most were male patients and had significantly higher serum levels of uric acid and creatinine than the other patients. Gender and renal function were the major determinants of serum uric acid in elderly hypertensive patients.