The dusky fruit bat Penthetor lucasi is a small and poorly known species (Megachiroptera, Pteropodidae) inhabiting Southeast Asia. I studied its reproduction in Brunei, northern Borneo, where individuals were usually captured in rainforest. The climate of the study area is characterized by uniformly high temperatures and rainfall, but with two seasons of greater rainfall (April to July and October to December) and two of lesser rainfall. Based upon my data, I estimate the following regarding reproduction of P. lucasi. In general, reproduction of P. lucasi is characterized by a synchronized birth season around the month of October. Birth is followed by a postpartum estrus and mating; 2-4 months of lactation; a prolonged period of delayed embryonic development; and then relatively rapid embryonic development from July to September, with the subsequent birth likewise around October. In sum, the reproductive cycle is consistent with a pattern of seasonal monestry. The synchronized birth season of P. lucasi does not correspond to the season of abundant flowering/fruiting (April to June) at the study site; rather, the species was relatively absent during this time. Thus, reproduction of P. lucasi appears linked to the flowering/fruiting and availability of specific plant species. This conforms to the concept of a sequential food specialist in which a species uses only a small and select fraction of the plants that are flowering/fruiting at any period of time. Females become sexually mature when weighing approximately 33.0-34.0 g in body mass with forearms approximately 5.7-6.2 cm in length. Males attain sexual maturity at approximately 27.0-30.0 g body mass with forearms approximately 5.4-5.8 cm in length. Seasonal testis recrudescence was not observed.