The purpose of this paper is to examine variations in the use of international integration mechanisms across individual human resource management (HRM) practices in MNCs. Drawing upon data from a sample of over 450 MNC subsidiaries located in Ireland and Spain and an ordinal regression methodology, several models were tested. he findings provide evidence that people, information and formalized-based mechanisms are positively related to the use of centralization-based integration processes. The results also demonstrate that the use of personal-based integration mechanisms is uniform across the suite of individual HRM practices among those MNCs where an international HRM committee is present, while the deployment of expatriates does not prove to be particularly significant in achieving integration across the range of HRM practices examined in the model. Information- and formalization-based mechanisms hold explanatory power in relation to performance appraisal systems and compensation practices. This paper offers a comprehensive analysis of the preferred modes of integration across HRM practices in MNC subsidiaries located in two different institutional environments. The authors reveal how modes of integration vary for different HR domain areas and the authors provide explanations for this variation.