In a group of 129 obese men and women asymptomatic hyperuricaemia was found in 49 and gout in 30 patients. Moderate positive correlation between serum uric acid level and body mass index was observed. Serum uric acid level was higher in all groups of obese patients than in the control group. The mean rate clearance was significantly decreased in obese patients with hyperuricaemia and gout. The most prevalent was the metabolic type of hyperuricaemia found in 58% of males and in 43% of females, followed by the mixed type (in 27% of males and in 29% of females). The renal type of hyperuricaemia was found in 15% of men and 28% of women. A significant increase in beta2-microglobulin in serum and urine of patients with hyperuricaemia and gout was determined by the radioimmunologic test. These results point to the incipient kidney lesions.