This article examines parallel models of union joining and leaving using individual-level longitudinal
panel data collected over a 5-year period. The authors utilized objective measures of joining and leaving
collected from union and organizational records and took into account time by using event history
analysis. The results indicated that union joining was negatively related to procedural justice and higher
performance appraisals and positively related to partner socialization and extrinsic union instrumentality.
Conversely, members were most likely to leave the union when they perceived lower procedural justice,
where there was no union representative present in the workplace, and where they had individualistic
orientations. The authors discuss the implications of these findings for theory and practice for trade
unions.