The purpose of this thesis is to contribute knowledge to the reintroduction program for Javan gibbons (Hylobates moloch) in West Java, Indonesia in an effort to improve the conservation of the species in the wild. Reintroduction programs provide an opportunity for animals that have lived in captivity to have another chance at living in the wild, and may be one way of reestablishing populations that have become locally extinct. It is crucial that release candidates either maintain or develop the appropriate behavioral repertoire necessary for living in the wild, and have undergone an extensive period of rehabilitation. My research goal was to examine whether select pairs of Javan gibbons living at the Javan Gibbon Rescue and Rehabilitation Center (JGC) in Gunung Gede-Pangrango National Park, Java, Indonesia exhibit the appropriate behaviors necessary for survival before they are released back into the wild. Behavioral data were collected from July to November 2009, yielding a total of 337 hours. I conducted pre- release behavioral observations on three pairs of Javan gibbons that were deemed potential candidates for release by the staff of JGC. I observed each individual gibbon utilizing focal animal time-interval sampling and ad libitum as necessary. I also conducted post-release observations on the first pair of Javan gibbons released in October 2009. Pre-release results indicate the pairs of Javan gibbons in this study did not satisfy all of the suggested behavioral criteria. However, the behavior that did not match the recommendations (time spent in positive pair association) will not necessarily hinder the gibbons' survival when they are released. It is recommended that rehabilitated gibbons spend at least 7% of total time active engaged in positive association behavior (i.e., groom, play, and copulation); not one of the pairs of Javan gibbons in this study met that criteria. This specific criterion was determined to not be a valid measure with regards to pair-bond cohesiveness, because it fails to include maintenance of close-proximity - one of the primary social interactions for adult gibbons. In addition, the other behavioral criteria the gibbons did satisfy (i.e., effectively brachiating, remaining in upper level of enclosure, feeding/foraging) are those that will be most beneficial for their survival in the wild. Post-release observations indicate that the gibbon pair was successful at locating and procuring the appropriate food sources. They jointly defended their territory against sympatric monkeys, and they remained in the upper level of the canopy. Most importantly, the pair remained together after release and the female regularly vocalized. However, the gibbons exhibited a high level of aggression towards human observers. The results from this thesis can inform a revision of the proposed recommendations for evaluating the behavioral preparedness of rehabilitated gibbons. Based on the overall behavioral profile of the released gibbons, it would seem that at least some Javan gibbons are capable of acquiring the necessary survival skills to live in the wild after a period of rehabilitation. At the same time, considering the aggressive behavior that the gibbons displayed towards humans, caution must be taken for future observation and monitoring of reintroduced Javan gibbons and future release sites should have very minimal human activity.