The authors explore whether employees' willingness to perform organization citizenship behavior (OCB), or go “above and beyond” what is required by their jobs, is affected by social influence. The authors draw on social information processing and social learning theories to argue that OCB is contagious, or affected by the OCB of employees with whom a focal employee maintains social network ties. A study of admissions department employees reveals that strong advice ties between employees are positively and significantly related to similarity in OCB, whereas strong friendship ties and weak ties are not. Implications for research and practice, including suggestions for influencing ethical behavior in organizations, are discussed.