AbstractIn general, previous research suggests that the primary determinant of union members' level of union commitment is their satisfaction with the union's ability to secure desired levels of various work‐related outcomes (wages, benefits etc.). This research is consistent with a social exchange based view of union commitment. Eisenbergeret al.(1986, 1990) obtained support for the idea that social exchange is not entirely economic: perceptions of organizational support predicted several criteria. This study sought to extend organizational support perceptions to the union setting and test the relative contribution of members' perceptions of union support and instrumentality to prediction of union commitment. Hypotheses were tested by surveying 77 employees of a small northeastern state university. Results of correlational and multiple regression analyses indicated that perceptions of union support accounted for more variance in union commitment than did union instrumentality. This result held for the union's instrumentality relative to both traditional bargaining issues and issues important only to faculty members. However, contrary to predictions, exchange ideology did not moderate relations between union instrumentality and union commitment or between union support and union commitmen