Spermatogenesis in the non-scrotal, insectivorous microchiropteran, Rhinopoma kinneari Wroughton, is a cyclic phenomenon. It comprises (i) eleven cell associations, and (ii) 16 evolutive steps in spermiogenesis. In the seminiferous epithelium, spermatogonia of the A, intermediate (In), and B type are characteristically present. Leptotene, pachytene and diakinesis stages were easily discerned in dividing spermatocytes. During the 16-step spermiogenesis, the acrosomic system develops through the Golgi, cap, acrosome and maturation phases. The relative frequency of various cell associations differs markedly and is significantly at variance with other mammalian species. Fully formed spermatozoa are dimorphic with conical or blunt heads.