The endangered Indiana bat (Myotis sodalis) has declined dramatically and continuing threats have made it necessary to understand population dynamics and life history throughout the year. Specifically, demographic information (e.g., population size, reproductive success, survival) from the summer range where females raise their young in maternity colonies is difficult to estimate precisely using traditional techniques (such as emergence counts). Further, the familial makeup of maternity colonies is unknown. Genetic mark-recapture methods are increasingly being used to estimate demographic parameters in species where traditional techniques are problematic and can also provide insight into relatedness among individuals. Therefore, our objectives were to: 1) use genetic mark-recapture to provide estimates of survival, detection probability and population size of Indiana bats at a maternity roost in Indianapolis, IN, 2) compare population size estimates using genetic mark-recapture with emergence counts collected at the same roost tree, and 3) document levels of relatedness among individuals. In the summer of 2008, we collected fecal pellets and conducted emergence counts at a prominent roost tree during three time periods each lasting seven or eight days. We genotyped fecal DNA using five highly polymorphic microsatellite loci to identify individuals and used a robust design mark-recapture approach to estimate detection and survival probabilities as well as population size at the roost. Emergence count estimates ranged from 100 - 215, whereas genetic mark-recapture estimates were higher ranging from 122 – 266 and more precise (with smaller confidence intervals). Apparent survival was 0.994 (SE=0.04) between sampling periods suggesting that few bats died or permanently emigrated during the course of the study. Relatedness estimates, r, between all pairs of individuals averaged 0.055 ranging from 0 – 0.779 indicating that most individuals were not closely related. We demonstrate here the promise of using fecal DNA to estimate demographic information for Indiana bats and potentially other bat species.