We present the quantitative description of spermatogenesis in a 4.5-year-old boy with precocious puberty, where Leydig cell hyperplasia was associated with excessive secretion of testosterone (T), but predominantly with estradiol (E). The results were compared with data obtained from an age-matched group and adult men without hormonal abnormalities. We showed, that excessive secretion of T and E with relative deficiency of FSH is sufficient to induce testicular tubule maturation and qualitatively complete spermatogenesis, although with a poorer quantitative aspect.