In 30 male Chacma baboons, prepubertal, pubertal, and adult animals have been identified by their testicular and prostatic weights. The volume of the stromal and epithelial components of caudal prostate were calculated from morphometric determination of the percentage volume of each component and the total caudal prostate volume. Both stromal and epithelial volumes increased at puberty and plateaued at maturity. These increases could be fitted to logistic curves that support the conclusion that stromal pubertal growth precedes epithelial pubertal growth. The stromal contribution to prostates of increasing size followed a model distinct to that of the epithelial contribution, thus suggesting that the factors (e.g., androgens) controlling stromal and epithelial growth are not identical. Stromal growth may be a prerequisite for pubertal epithelial development of the prostate.