Insectivorous bats have rarely been considered suitable as breeding laboratory animals despite their unique reproductive physiology. The purpose of this study was to compare maternal care and growth of young in several species of British vespertilionids in order to find one or more species that would adapt well to conditions of captivity. During the spring of 1966 and of 1967, 17 noctule (Nyctalus noctula Schreber), eight serotine (Eptesicus serotinus, Schreber), 33 pipistrelle (Pipistrellus pipistrellus, Schreber), and four long-eared (Plecotus auritus, Linnaeus) bats were brought into the laboratory after insemination or when pregnant, and most gave birth. One noctule mated in the laboratory in the autumn of 1966 and gave birth to twins in June 1967, thus providing the first known breeding record of any British vespertilionid in captivity. Noctules (13) housed in near natural conditions with limited food gave birth four weeks after others (four) fed ad lib. and housed in a room which buffered the changes in external temperature, and two long-eared bats gave birth in late May (the normal birth season is June to July). These early births may have resulted from premature ovulations and/or a shortened gestation. Fourteen of 17 live-born noctules, all live-bom serotines (four), 12 of 14 live-born pipistrelles, and none of the long-eared bats were reared to weaning age. As part of maternal care all females allogroomed and retrieved their young until the second week post-partum, and recognition of offspring seemed to be effected primarily by sound and individual odour. Neonates of three species were about 20% of the mother's weight at birth and doubled their weight by the end of the second week. Forearm growth ceased at approximately five weeks of age. Weaning, which was assisted, was completed by the end of the second month and adult weight was reached soon thereafter. The development of the three species, i.e. the opening of the eyes, hair growth, and the replacement of the deciduous teeth, differed, and the pipistrelles and serotines developed more rapidly than the noctules.