Light microscope and ultrastructural studies of normal infants and children testes revealed the presence of primary spermatocytes and occasional spermatids at 4, 8, 9, 11, 12 and 13 years of age, but not in all the boys of these ages. When they were found they appeared in both testes, but only in a 5-25% of the seminiferous tubules. These spermatocytes undergo degeneration or progress to abnormal spermatids which degenerate in turn. Spermatozoa were never found.