Patterns of reproductive phenology and temporal variation in species composition and age structure were investigated for a sample of terrestrial leaf litter frogs from a lowland tropical rainforest in north-eastern Costa Rica. Recruitment of most species showed a seasonal pattern in which the growth of juveniles occurred during the dry season. The phenology of the assemblage was also seasonal, with a peak in abundance during the dry season. Variation in abundance was driven by seasonal patterns of juvenile recruitment in one species, Eleutherodactylus brandsfordii. We suggest that the timing of reproduction and patterns of frog phenology may be tied to the availability of arthropod prey items. A comparison of our data with data collected at other rainforest sites in Central America and the Amazon basin of South America indicates that patterns of recruitment and abundance, while correlated with arthropod abundance on both continents, show divergent seasonal patterns. This and other studies indicate that peaks in abundance and recruitment of juvenile frogs are concentrated in the dry season in Central America, whereas in South American rainforests, the wet season is the period of highest abundance and juvenile recruitment. We suggest that the length and severity of dry periods in the Amazon basin limits the ability of terrestrial frogs to reproduce successfully, while in Central America a more benign dry season, while strong enough to create distinct seasonal trends in the phenology of rainforest animals, is not strong enough to prohibit frogs from recruiting juveniles during the dry season.