In response to new emphasis by regulatory agencies regarding socialization, behavioral management programs are allocating greater resources to maximize socialization opportunities for laboratory primates. Information regarding predictors of compatibility and risk of injury for all laboratory-housed species of macaques are needed to make social introductions and pairings as efficient and safe as possible. This study presents data on 674 pairs of pigtailed macaques (Macaca nemestrina) at the Washington National Primate Research Center over a 7-year period. During pair introduction, behavior was monitored while the degree of tactile contact was gradually increased. Based on observed behavior, pairs were assigned a behavioral introduction score (BIS), rating the quality of their interactions for each day of introduction. Animals deemed compatible, based on the BIS and technologist judgment, were allowed to progress to continuous contact with no staff present. A small proportion of animals deemed compatible at introduction was later separated for subsequent incompatibility or aggression; these proportions were higher in full contact compared to protected contact pairings. Of 674 pairs, 75% were deemed compatible at introduction in protected contact; 86 of these pairs were later transitioned to full contact with 98% compatibility. Predictors of decreased compatibility assessed during protected contact introductions included age (adult pairs were less compatible), the BIS on the last day of introduction, and aggression or injury during the introductory period. Predictors of injuries during the protected contact introduction process included: aggression on the first day of introduction, a negative BIS on the first or last day of introduction, and, surprisingly, the presence of grooming on the first day of introduction. Injuries during both introduction and subsequent pairing in protected contact were rare; however, injury rates increased significantly during full-contact pairing. These findings underscore the necessity of species-specific data to guide decision-making during the social introduction process. Am. J. Primatol. 79:e22556, 2017. © 2016 Wiley Periodicals, Inc.