This study explores the relationship between implementation variables and performance improvements of ERP systems. DeLone and McLean's (1992) information systems (IS) success framework is adopted to develop performance measures to evaluate improvements in the performance of ERP systems after implementing ERP systems. The implementation variables investigated in this study are the ERP implementation status, ERP system source and ERP implementation strategy. Structured questionnaires were sent to companies listed in the top 5000 largest corporations of Taiwan. The research findings indicate that the strongest ERP systems performance improvement comes from companies that implement non-packaged ERP systems, using integral planning, and employing all the planned ERP modules.