Serum urate levels and history of gout were observed from 4663 men aged 20-44 who were employed by a Parisian government agency. Serum urate levels, mean value 62,8 mg/l (374 mu mol/l), did not vary with age but were strongly correlated with weight. For constant weight, urate levels decreased with age. By our definition: typical history of gout and either efficacity of colchicine during an attack or serum urate level over 70 mg/l (417 mu mol/l) at examination, there were 57 cases of gout, giving a prevalence of 1,1% among men 35-39 and 2,0% among men 40-44 years old. Using the definition by the New York criteria which do not include serum urate level, there were 51 cases of gout, giving a prevalence of 1,5% in the 35-44 year age group. This is about 3 times the prevalence found by O'Sullivan, using the same criteria, in an American town. the higher serum urate levels in the present study may account for much of this difference. The incidence of new cases of gout was estimated to be 1,6% over 5 years for men 40-44 years old. The site was the great toe in 57% of gouty men with only one attack and in 92% of those with more than one attack. It was not related to the amount of standing or activity at work. Comparison with a study made 7 years earlier showed an augmentation in serum urate values and probably in prevalence of gout. These results are discussed in terms of dietary modification over this time period.