Tropical microchiropteran bats need to seek out environments of thermoneutrality which in the tropics, of course, may mean selecting ‘cooler’ places for the diurnal roosts. Thus the roosting sites of all the species studied,Rhinopoma hardwickei, Taphozous melanopogon, Hipposideros speoris, Hipposideros bicolor andMegaderma lyra inhabiting caves, caverns, interiors of temples and a cellar were cooler by several degrees and showed a relatively constant temperature than outside in the open. Such a lower and relatively constant temperature found in the roosts apparently aid in lowering the metabolic rate and cost and may be vital in these tropical species that do not hibernate and some of which may be (such asHipposideros speoris) continuous breeders. This paper presents the temperature and light intensity profiles of bat roosts over 24 h periods for the course of an entire year. It is found that physical protection from predators, relative constancy of temperatures, lower levels of illumination and high humidity seem to determine the choice for roosts in these species of bats.