Knowledge about distribution of primate species and their densities is crucial for conservation and management. However, such information is often lacking or anecdotal, even for seemingly abundant species. Long-tailed macaques (Macaca fascicularis) are distributed across southeast Asia and recognized by the International Union for Conservation of Nature Species Survival Commission Primate Specialist Group (IUCN SSC PSG) as both widespread and rapidly declining. Precise local density and abundance data are scarce across their range. To provide density and abundance estimates for a long-tailed macaque population we conducted line transect distance sampling throughout Baluran National Park (250 km(2)), East Java, Indonesia covering all habitats. Long-tailed macaque density was 41.4 ind/km(2) (95% confidence interval, CI: 23.04-74.39), with an estimated abundance of 10,350 individuals (95% CI: 5,760-18,598). A density of 41.4 ind/km(2) is lower than previous estimates for other sites in Java. Species distribution and habitat suitability analysis revealed a macaque preference for areas close to or on roads and trails, invasive acacia and/or native savannah. Long-tailed macaques were provisioned with human food by commuters and tourists along roads and trails, probably structuring their distribution/habitat use. To evaluate if long-tailed-macaques have been overestimated for years, we also conducted a nonrandom point distance sampling survey according to macaque presence restricted to roads and trails. This survey provided density and abundance results much higher than the line transect distance sampling survey. Our study provides much needed baseline data for this species. Baluran National Park management and management in other areas can use these results to create informed management decisions regarding long-tailed macaques. We recommend conducting systematic surveys of long-tailed macaques throughout their range, and possibly reassessing conservation status, and conservation and management measures for long-tailed macaques.