Over-winter roosting sites for Eastern Bent-wing Bats Miniopterus schreibersii oceanensis occur in urban areas including parts of greater Sydney. Most of the known over-winter roost sites in Sydney are located in the northern and western suburbs (Hoye and Spence 2004). Only one roosting site was known to exist in eastern Sydney at La Perouse (Henry Head). In January 2004, a second roosting site was identified in the eastern Sydney, on the headland at Malabar. Both sites are close to the coast and are disused military tunnels and underground rooms that can be used by the bats. Routine monitoring surveys were set up to determine the significance of the Malabar site and whether bats from Henry Head also use the Malabar site. Searches were made for other bat roosting sites, and a third site, at Cape Banks, was later found. Apart from recording bat numbers during each survey, wind speeds at the entrance to the roosting sites and air temperatures inside the roosts were measured. It was concluded that all three sites were used by a single population of Bent-wing bats: Cape Banks rarely contained roosting bats, Henry Head was occupied more regularly whereas Malabar was occupied the most often. Cape Banks was the most wind- exposed site, Henry Head was partly exposed to the wind while Malabar was the least exposed site. Malabar also had the warmest roost temperatures. Bat numbers at each site were associated with prevailing weather conditions, with higher numbers of bats at Malabar during stormy conditions. Bent-wing bats arrive at the eastern Sydney sites in late February or early March and remain there throughout the winter. They depart in October and November, much later than has been reported for bats elsewhere in Sydney. In March 2005, two female bats were observed with young at Malabar, suggesting that the summer maternity roost may not be far from the eastern suburbs over-winter sites. Conservation measures are needed to protect the Malabar roost site from intruders and vandalism. Human disturbance of the roosting bats has been responsible for the bats periodically vacating the site.