The spermatogenic cycle of Tantilla coronata is post-nuptial. Spermatogenesis begins in May and reaches a peak in July and August. The sexual segment of the kidney has a cycle opposite that of the testis. Hypertrophy of the sexual segment occurs in the early spring (May) and summer july-September). Mating occurs during the period of sexual segment hypertrophy. The youngest males examined (approximately 1 2 months of age) begin spermatogenesis at the same time of year as adults, and the course of spermatogenesis appears similar to adults. It appears, however, that insufficient sperm are produced to permit successful mating following the first spermatogenic season. During the second spermatogenic season, enough sperm are produced to permit mating in the summer or following spring.