The African fruit bat, Eidolon helvum Kerr, is known to occur only south of the Sahara where its distribution is localized. At 0°20′ N, this bat exhibits seasonal and synchronized breeding the rhythm of which appears to correspond with the two rainfall peaks typical of Uganda. Quite unexpectedly and unprecedently, this bat exhibits delayed implantation lasting about three months. Evidence for this phenomenon comes from the histological examination of the adult female genital tracts which indicate that mating occurs only in April-June, but implanted embryos are only in evidence in October-November. The male sexual cycle corresponds to such a rhythm and shows a maximum testicular weight at the mating time. Births take place in February-March thus giving a gestation period of about four months. Only one young is born at a time and births occur just before the onset of the higher of the two rainfall peaks, presumably creating favourable conditions for the maximum survival of the young bats when weaned.