The contents of the annual reports of listed mining companies as well as of the Top 100 industrial companies in South Africa were analysed to determine how the disclosure of environmental information has changed over time. Disclosure of general environmental information increased until 1999 and then stabilised at that level. The initial increase in the disclosure of specific environmental information, such as measurable objectives and environmental performance, was followed by a decrease from 1998 onwards. A possible explanation could be that the lack of legal requirements with regard to the reporting of environmental information enables companies to decide what to report and what the extent of the reporting should be. They can therefore elect not to report specific and sometimes sensitive information, because stakeholders could perceive such information to be negative and it could therefore have a negative impact on the corporate image.