For more than a decade, researchers have studied the phenomenon of affective commitment and of its determinants. To our knowledge, no research has studied the variation of the determinants of affective commitment over time. Our research studies the impact of changes made to three HRM systems on the variation of the affective commitment of employees in a Regional Health and Social Services Authority between 1999 and 2002. The research problematic is based on Rousseau’s psychological contract theory (1995), according to which organizational changes modify the terms of the employment relationship, and these make it possible to improve the terms of the work contract, that is to say, the psychological contract of the employee. In response to these improvements, the employee adjusts his behaviours and his attitudes. The general research hypothesis is that changes in the perception of empowerment, of organizational justice and of career plateauing have a positive impact on the development of affective commitment. So as to verify this general hypothesis, specific hypotheses apply to the analysis of the link between each of these factors on affective commitment at two separate points in time, in 1999, and in 2002. Regression analyses make it possible to evaluate these hypotheses and subsequently, interviews were carried out with employees in order to interpret these statistical analyses. The results of the variance analyses reveal that the employees are more autonomous and participate to a higher degree in the decision-making processes, that procedures are more impartial and that employees are less plateaued in the hierarchy in 2002. These improvements in Human Resource Management go along with an increase in the level of affective commitment in 2002: the employees are, at this point, very committed, and highly identify with organizational values and business objectives. As well, these organizational changes make it possible for structural plateauing and interactional justice to become significantly linked to commitment in 2002. Otherwise, only content plateauing is significantly linked to affective commitment in 1999, and 2002. Thus, career plateauing absorbs the influence of the other HRM systems, and these are not significantly linked to commitment. Before setting up mechanisms to empower employees or to improve the impartiality of processes and interactions within the business, managers would be well advised to put in place mechanisms to manage their employees’ careers. This is because plateaued employees, whether this be in their work content or within the hierarchy, are disengaged from the organization, and efforts applied to other HRM practices may be without effect on affective commitment. The implications and the limits of these results are discussed
