We investigated the distribution of tenascin during postnatal development of the human prostate. Monoclonal antibody specific to human tenascin was applied to paraffin sections by the avidin-biotin-complex method to examine its localization. Infantile prostates showed two distinct zones. The inner zone had sparse acini with fibromuscular bundles. The peripheral zone had similar acini and lighter stroma as compared with inner zone. Tenascin was found diffusely but weakly. The periglandular area occasionally showed immunoreactivity. The prostates from 9- to 13-year-old subjects had a morphology similar to that of the infantile gland. The difference was increased density of the acini. Immunoreactivity was low. In the prostates from 14- to 21-year-old subjects, the acini distribution was more crowded, and the epithelial lining had become taller in both zones. Tenascin distributed preferentially in the peripheral zone during this period. Simultaneously, the percent of glandular area in the peripheral zone rose abruptly. The dynamics of tenascin expression are closely associated with the development and maturation of the gland. The distribution of tenascin during the post-puberal period may suggest its participation in the preferential of prostatic carcinoma in the peripheral zone.