1. The duration of individual stages of meiosis and spermiogenesis in Channa punctatus (Bloch) was calculated autoradiographically by using the kinetics of H³-TdR labelled spermatocytes in vivo.
2. The duration of leptotene, zygotene, diplotene, diakinesis and metaphase I is short while that of pachytene is in between 1.95 and 2.20 days.
3. The spermiogenesis is completed within 7.80±0.20 days and the labelled spermatozoa were detected at 11.25 d post injection, which is the approximate total duration of meiosis and spermiogenesis.
4. The ratio of the total meiotic duration to that of spermiogenesis shows statistical agreement with the frequency of occurrence of all meiotic stages and spermatids in the seminiferous tubules.