This article attempts to assess the impact of Socially Responsible Investing (SRI) on stock prices, and thus the pressure exerted on firms. To do so, the effects on stock prices of inclusion in and exclusion from SRI indexes are measured. This study draws on an event study carried out from 827 stock index redefinitions for three SRI index families: FTSE4Good, DJSI, and Aspi. The authors find that no significant impact results from the announcement of such redefinitions, except for the Aspi index. But stocks included in SRI indexes experience a temporary and significant positive abnormal return, which attests to the influence of SRI passive funds managers. Also, it appears that this short-term impact is stronger for U.S. firms, which is consistent with the respective national weights of the SRI practices.