Fogarty International Clinical Research Scholars Program: National Institutes of Health, USA and the Departamento Administrativo de Ciencia, Tecnología e Innovación COLCIENCIAS, Colombia (Cod 325645221265 – 352-2008)Naturally acquired acute leptospirosis in monkeys is uncommon. This study reports an outbreak of severe leptospirosis among 52 capuchin (Cebus) monkeys that had been rescued from homes and housed in a wildlife rehabilitation center in Colombia in 2007. Case confirmation consisted of Leptospira isolation followed by a polymerase chain reaction targeting the LipL32 gene. The attack and mortality rates were 71% and 27%, respectively. Sixteen cases were confirmed. Necropsy revealed diffuse jaundice and pulmonary hemorrhage. Multi-locus sequence typing identified the agent to be Leptospira interrogans sequence type 17, indicating rats as the source of infection. An environmental survey confirmed rodent infestation as the cause of the outbreak. The extent of Leptospira transmission between humans and monkeys is unknown. Improper husbandry of non-human primates could create new reservoirs and transmission routes for Leptospira threatening conservation efforts and public health.