摘要：This study aims to determine the window of event which best explains the relationship between the adhesion or migration to the Differentiated Levels of Corporative Governance ( DLCG) of the BM&FBovespa and the valuation of company stocks. For that, the event study method was adopted, with the adoption of and the Statistical Model of Market was chosen adopted to determine the optimal size of the event window for the relationship between the adhesion or migration to the DLSG and to stock valuation. Windows of different sizes were set within the range of 70 trading sessions around the event. In 49.3% of the cases, there was at least one window in which the effect of the event was significant. The results line up to previous studies by indicating abnormal returns, though they are not enough to determine the window which effectively represents the relationship between the adhesion or migration to DLCG and the stock valuation.
