The diel and seasonal calling activities of anurans are regulated by several environmental factors. We studied the effect of environmental factors on patterns of calling behavior of six sympatric frogs in an area of Atlantic rain forest at Ilha Grande, south of Rio de Janeiro state, Brazil. The number of calling males and the number of calls of each species were recorded at hourly intervals from October 1998 to September 2000. Two analyses were performed: hourly calling behavior of males of each species was related to air temperature, and monthly calling was related to air temperature and cumulative short-term rainfall. Males of Leptodactylus marmoratus, Aplastodiscus eugenioi, Physalaemus signifer, Scinax hayii, and S. trapicheiroi called mainly at night, whereas male Ischnocnema parva called mostly at dusk and dawn. The species studied at Ilha Grande rain forest called mainly in the wettest and warmest months. Scinax trapicheiroi, P. signifier, and A. eugenioi called throughout the year. Leptodactylus marmoratus was the only species whose calling behavior was restricted to a few months. Air temperature had a significant effect on the hourly number of calls for L. marmoratus, A. eugenioi, S. hayii, and S. trapicheiroi, and rainfall had a significant effect on the monthly number of calls of I. parva.