Roosting behavior and the reproductive chronology of the banana bat, Pipistrellus nanus, were studied in Natal, South Africa. These bats roost singly or in small groups in rolled leaves of bananas (Musa sp.) and Strelitzia. Sex ratios were 1:1 for adults but 2:1 (female:male) in juveniles. Group structure was facultative and ephemeral, and movements were for short distances. P. nanus is monestrous and seasonal, with births of single or twin infants in November and December. Males reached peak testis size in May, and had abdominal testes most of the remainder of the year.