Several South-East Asian anuran species can breed year-round near the equator (due to abundant rainfall in all months in Singapore, for example) but are limited to a 6-mo breeding season in other areas (including central Thailand). In order to investigate the extent to which such differences in breeding season length are associated with differences in reproductive measures such as clutch size, reproduction of three common species, Polypedates leucomystax, Microhyla heymonsi and Hylarana erythraea, was compared in Singapore and Thailand over a 2-y period. All three species produce nearly twice as many eggs per clutch in seasonal environments compared with aseasonal environments, although annual fecundity may be similar in both environments. In Polypedates leucomystax, increased clutch size and volume are associated with larger female size, but in the other two species female size is unchanged with respect to latitude. In H. erythraea, the increased clutch size in Thailand was observed early in the breeding season; later clutches were not significantly different between sites. Collectively, these data suggest that these widespread species have adapted to shortened breeding season length by increasing clutch size.