ERP systems have long been known for their significant impact on the adoptingcompanies, irrespective of size and industry. To better understand and maximize thepositive impacts, ERP research has mostly focused on the selection, evaluation andimplementation stages. Failure rates, however, indicate that post--implementation isanother essential stage for the success of ERP projects. Based on a qualitativeresearch design using case-study methodology, this study investigates thedeterminants of ERP assimilation success during the post-implementation stage. Thispaper compares three Tunisian manufacturing companies with three Canadianmanufacturing companies and presents the lessons learned from this analysis.