This survey-based field study of 257 service employees developed and tested a model of differences in the organizational citizenship behavior of full-time and part-time employees based on social exchange theory. Questionnaire data from matched pairs of employees and their supervisors demonstrated that part-time employees exhibited less helping organizational citizenship behavior than full-time employees, but there was no difference in their voice behavior. We also predicted that both preferred work status (an individual factor) and organizational culture (a contextual factor) would moderate the relationships between work status and citizenship. For helping, results demonstrated that preferred status mattered more to part-time workers than to full-time. For voice, preferred work status was equally important to part-time and full-time workers, such that voice was high only when actual status matched preferred status. Contrary to our expectations, work status made more of a difference in both helping and voice in less bureaucratic organizations. We discuss the implications of work status for social exchange relationships, differences in the social exchange costs and benefits of helping compared to voice, and ramifications of our findings for future research. Copyright © 2001 John Wiley & Sons, Ltd.