Serum uric acid (SUA) was measured in 512 men and 254 women from two English regions and in 337 men from one Scottish region. Mean SUA levels were the same in the men (5-5 mg/100 ml) and similar in the women (3-9 and 4-1 mg/100 ml). The apparent rarity of gout in Scotsmen cannot be explained by regional differences in SUA levels or in the prevalence of hyperuricaemia (defined as SUA of 7-0 mg/100 ml or over) which was present in 6-6% of the English men and 8% of the Scots. SUA was positively correlated with weight and serum urea, and with age in women, but no variation was found with social class. Body weight was the most important predictor of SUA in both men and women and superior to measurements involving correction for height, such as ponderal index and calculated lean body mass.