This paper surveys the economic literature on Corporate Environmental Responsibility (CER). It first defines and illustrates what CER is, and what it is not (namely green washing). It then examines various rationales for firms to implement CER programs: to respond to social pressure, pre-empt regulations, strategically differentiate from competitors, raise entry barriers, retain and motivate employees, lower the cost of capital, promote discipline and good governance, and foster innovation. Whether implementing CER enhances economic welfare is considered next. The paper ends by sketching what appear at this point to be some worthwhile research directions.