1. The total hydroxyproline: creatinine ratios in random urines collected every 3 months for 1 year from twenty-six adolescent boys (11-14 years) have been compared with the observed height and weight velocities of the boys during that year. 2. There were significant correlations of both height and weight velocities over 6 and 12 month periods with the ratios in the random urines collected duri...