Infannt cebus monkeys, removed from their mothers shortly after birth, were reared in a primate nursery on diets of controlled nutritional quality. At regular intervals between birth and one year of age, each monkey was anesthetized, measured, and radiographed. Measurements were fitted to functions of the animal's age in days; a linear function for the first 6 to 8 weeks and a logarithmic function for the remainder of the first year. Mean constant curves have been calculated for each measure and estimates of animal variability have been obtained by interpolating sizes at given ages from regression lines fitted to the data for each animal. The maximum rate of growth was attained soon after birth. Cranial-caudal and distal-proximal maturity gradients in size attainment were observed.