Urate levels were assayed in sera of 292 subjects between 10 and 14 years of age identified through a probability sample of a natural population. The sex trends in serum urate concentrations characteristic of childhood were seen to continue into early adolescence, with girls maintaining slightly higher means. Between 10 and 14 years there was first an overlap of male and female values followed by a reversal of trends, with much higher means in boys. Serum urate concentrations peaked in girls at age 11 and gradually stabilized at lower levels. Boys, on the other hand, showed little age variation in serum urate at 10 and 11 years but by age 12 showed sharp upward trends which continued throughout adolescence. Since age and body weight are known to be important covariates of serum urate, boys were matched to girls of the same age and body weight. Significant sex differences in urate levels persisted (after matching) only for 14-year-old adolescents and thus at this age could not be ascribed to weight differentials. The study highlights a peripubertal phenomenon whose mechanism might be endocrine related.