scale resulting from the market performance post mergers and acquisitions might not necessarily make up for all the costs within a short period of time; ultimately, the cost sav - ing from both firms makes notable and direct improvement in firm financial performance and the market performance post Merger and Acquisition has a positive impact on the improvement of financial performance. The results also show that the mergers and acquisi - tions from foreign investors create more notable cost savings than those of domestic investors and it is mainly due to the introduction of new technology and equipment and the application of manage - ment system. Key Words Merger and Acquisition; Extent of Integration; Speed of Integration; Firm Performance 154-160