Three bat communities were studied for 1 year at each of two localities in the Panama Canal Zone and one locality in western Costa Rica. Removal sampling and banding techniques using Japanese mist nets were employed to document community structure, food habits, reproductive cycles, and movement patterns of these bats. Results indicated that 27—31 species occur at or near ground level at each locality. Species diversity, as measured by H', was highest in the Costan Rican community; each community contained 3—4 common species and many uncommon species. Based on body size and general food habits, niche overlap appears to be greatest among small to intermediate—sized insectivores and frugivores, many of which, however, are apparently uncommon. Four basic reproductive patterns are found among the species. Most frugivores are seasonally polyestrous whereas some insectivores are monestrous and at least one is polyestrous. It is postulated that in both insectivores and frugivores birth peaks coincide with maximum food levels. Recapture patterns of several species suggest that home range size may be positively correlated with body size; omnivorous species may have larger home ranges than similarly size species with more restricted diets.