_Natural History._--Throughout most of its range _Smilisca baudini_ occurs in sub-humid habitats; consequently the activity is controlled by the seasonal nature of the rainfall and usually extends from May or June through September. Throughout Mexico and Central America the species is known to call and breed in June, July, and August. Several records indicate that the breeding season in Central America is more lengthy. Gaige, Hartweg, and Stuart (1937:4) noted gravid females collected at El Recreo, Nicaragua, in August and September. Schmidt (1941:486) reported calling males in February in British Honduras. Stuart (1958:17) stated that tadpoles were found in mid-February, juveniles in February and March and half-grown individuals from mid-March to mid-May at Tikal, El Peten, Guatemala. Stuart (1961:74) reported juveniles from Tikal in July, and that individuals were active at night when there had been light rain in the dry season in February and March in El Peten, Guatemala. _Smilisca baudini_ seeks daytime retreats in bromeliads, elephant-ear plants (_Xanthosoma_), and beneath bark or in holes in trees. By far the most utilized retreat in the dry season in parts of the range is beneath the outer sheaths of banana plants. Large numbers of these frogs were found in banana plants at Cuautlapan, Veracruz, in March, 1956, in March and December, 1959. Large breeding congregations of this frog are often found at the time of the first heavy rains in the wet season. Gadow (1908:76) estimated 45,000 frogs at one breeding site in Veracruz. In the vicinity of Tehuantepec, Oaxaca, large numbers of individuals were found around rain pools and roadside ditches in July, 1956, and July, 1958; large concentrations were found near Chinaja, Guatemala, in June, 1960, and near Esparta, Costa Rica in July, 1961. Usually males call from the ground at the edge of the water or not infrequently sit in shallow water, but sometimes males call from bushes and low trees around the water. Stuart (1935:38) recorded individuals calling and breeding throughout the day at La Libertad, Guatemala. _Smilisca baudini_ usually is absent from breeding congregations of hylids; frequently _S. baudini_ breeds alone in small temporary pools separated from large ponds where numerous other species are breeding. In Guerrero and Oaxaca, Mexico, _S. baudini_ breeds in the same ponds with _Rhinophrynus dorsalis_, _Bufo marmoreus_, _Engystomops pustulosus_, and _Diaglena reticulata_, and in the vicinity of Esparta, Costa Rica, _S. baudini_ breeds in ponds with _Bufo coccifer_, _Hyla staufferi_, and _Phrynohyas venulosa_. In nearly all instances the breeding sites of _S. baudini_ are shallow, temporary pools.