The level of environmental disclosure and its relationship to actual environmental performance has been deeply examined during the past decade with controversial results. This thesis revisits the relationship between environmental disclosure and actual environmental performance while testing if these figures can be proxied by using carbon disclosure and carbon performance. I measure the environmental performance in 2008 of 144 companies from the FT global 500 by relating the total emissions reported in the CDP 7 to sales. Environmental disclosure is measured on the one hand by the Carbon Disclosure Leadership Index Score, published by the CDP and on the other hand by a score based on GRI reports. Evidence for socio-political theories is found, especially in environmental sensitive industries where the level of disclosure is higher. Since the investigation also includes the relation between carbon disclosure and carbon performance evidence for economics based theories was also found. It became clear that carbon performance can be used as a proxy to determine environmental performance but carbon disclosure does not serve as a predictor of environmental disclosure.