The content of the annual reports of listed South African mining companies from 1994 to 1999 was analysed to determine how many disclose certain environmental information. This number, expressed as a percentage, was compared with the corresponding percentage disclosure among the Financial Mail Top 100 industrial companies for the same years. A greater number of mining companies, when compared to other large companies, disclose environmental information. This finding is consistent with legitimacy, which is the notion that an organisation will not continue to prosper if its aims and methods are in conflict with that of society. Mining companies have a greater need to legitimise their operations by means of environmental disclosure, because their environmental impact is extensive and obvious.