Using a unique data set, I study how stock markets react to positive and negative events concerned with a firm's corporate social responsibility (CSR). I show that investors respond strongly negatively to negative events and weakly negatively to positive events. I then show that investors do value "offsetting CSR", that is positive CSR news concerning firms with a history of poor stakeholder relations. In contrast, investors respond negatively to positive CSR news which is more likely to result from agency problems. Finally, I provide evidence that CSR news with stronger legal and economic information content generates a more pronounced investor reaction.