The uricosuric effect of tiaprofenic acid was evaluated in a group of normouricaemic inpatients with various rheumatic disorders. Six patients aged 26 to 60 years were maintained on a standardised low-purine diet and, after a washout period of 72 hours, tiaprofenic acid was administered in 3 oral doses of 300 mg 12-hourly. A normal renal function, as assessed by serum creatinine and creatinine clearance determinations, was considered mandatory for entry into the study. The following parameters were evaluated before and after treatment: haematological values, blood urea nitrogen (BUN), serum and urinary creatine concentrations, serum uric acid concentration and the fractional excretion rate of uric acid. Our preliminary results showed a substantial increase of urinary uric acid excretion in the samples collected after treatment, especially in the first 4 hours.