Over the past four decades there has been a change in community attitudes towards the environment in Australia which has corresponded with an increase in environmental legislation and program development within Australia and internationally (Lothian 1994; Bates 1995; Welford 1999). During this period there has been an increase in the number of companies disclosing and in the quantity of disclosures made by those companies (Trotman 1979; Trotman & Bradley 1981; Gray, Kouhy & Lavers 1995b); however the quality and content of those disclosures has been questionable (Deegan & Rankin 1996; Guthrie & Parker 1990; Rockness 1985). In 1998 a new environmental reporting requirement was introduced into the Australian corporate landscape. The Australian Corporations Law was amended to include section 299(1)(f) which requires disclosing companies to include in the director's report information regarding compliance with relevant state or Commonwealth environmental regulations. However, many large companies and various industry groups resisted the requirement maintaining that implementation would result in increased compliance costs. Furthermore, voluntary reporting was espoused as the preferred method on the basis that market forces would prompt improvements in this area. Nevertheless, the mandatory disclosure requirement remains in place at this time. This paper extends the literature in the environmental disclosure area by providing the results of a study examining differences in the annual report disclosure practices of Australian companies under both a voluntary and mandatory environmental disclosure environment. The paper proceeds with a review of literature relating to annual report environmental disclosure practices, perceptions of current corporate environmental performance, and the introduction of mandatory environmental disclosure requirements in Australia. In the sections that follow, the reesearch proposition is developed; the research methodology is discussed; and finally the results and discussion are presented.