This study was conducted to examine the mechanisms involved in observed relations between human resource management (HRM) practices and employee commitment. Employees (N = 281) from several organizations completed a survey that included measures of (a) the quality of HRM practices pertaining to performance appraisal, benefits, training, and career development used in their organizations, (b) procedural justice and organizational support, and (c) affective, continuance, and normative commitment to the organization. Structural equation modeling analyses revealed that relations between employees' evaluations of HRM practices and their affective and normative commitment were largely mediated by perceptions of organizational support and procedural justice. These findings support previous claims that, although HRM practices can be valuable tools in the establishment and maintenance of employee commitment, their effects are neither direct nor unconditional.