This work investigated whether the mandatory adoption of IFRSs (International Financial Reporting Standards) had a positive impact on information asymmetry in ISE (Istanbul Stock Exchange). Using the bid-ask spread, trading volume and price volatility models, at first, the effects are investigated by descriptive analysis then the analysis continued using the OLS regression and the two-stage least squares regression method. Both the findings of regression analyses confirmed significant reductions in bid-ask spread subsequent to the adoption of the new accounting standards. The purpose of this study is to extend the spread decomposition literature into the order-driven environment. The dissertation, first research in Turkey to examine the impact of the mandatory adoption of IFRSs on information asymmetry in ISE, contributes to the literature by providing evidence on the economic link between increased accounting disclosure and information asymmetry in an emerging market. It also demonstrates that the accounting regulations permanently reduce long-run information asymmetry risk in capital markets.