Mergers and acquisitions remains the most utilized strategy for growth and expansion by firms worldwide. Nevertheless, a lot of doubts remain about the benefits of mergers especially to acquirers. While studies show that there may be initial benefits following merger deals to especially target firms and somewhat to acquirers, these benefits seem to erode in the long run for the latter. This book set out to investigate the above phenomenon among acquiring firms in the FTSE 100 index. In recent years, the corporate strategies of giant companies in the FTSE 100 index have contributed massively to the growing numbers of merger deals in the UK.For instance FTSE 100 index firms spent $645bn across 3,967 deals globally between 2003 and 2013. Increased pressures from the capital markets have caused managers of these firms to focus mainly on how to satisfy investors. They therefore resort to mergers and acquisitions (M&As) to improve performance and impress the financial markets. But havethese mergers and acquisitions been successful in the long run? The outcome of this study is vital considering how the FTSE 100 index is a vital indicator of the performance of the UK economy.