The main objective of company managers is to raise market power that is the market price of the company, and hence to increase profitability. The merger and acquisition activities, which is one of the restructuring processes relied on by companies in the world and Turkey are important to achieve this goal.   In this study, it is aimed to determine whether the acquisition activities of companies cause any change in various financial indicators of companies. Accordingly, it was also attempted to determine the financial ratios that present a significant change. In this context, Wilcoxon Signed Rank test was used in the SPSS-16 program to analyze whether there is a significant difference in the financial ratios caused by the acquisition activities of 10 companies publicly-traded on the Borsa Istanbul (BIST - Istanbul Stock Exchange) and had acquisition activities in 2004-2005. According to the results obtained, it was identified that assets turnover ratio, the net profit margin and leverage ratio of the companies significantly differed before and after the acquisition activities of the companies, however, no significant difference was found in the current ratios and average stock returns of the companies between these periods.   Keywords: Acquisition, Financial Ratios, BIST Jel Classification: G30, G32, G34