In Australia, there is growing interest in the potential for voluntary initiatives by industry to contribute to environmental policy objectives. This dissertation reviews the manner in which three different voluntary approaches (environmental management systems, the Greenhouse Challenge and the mining industry's Code for Environmental Management) have functioned, to assess whether or not voluntary approaches can lead to improved environmental outcomes compared to other policy instruments, and to define the conditions under which these improved outcomes can be achieved. The research indicates that the contribution of voluntary approaches is likely to be limited in situations where voluntary approaches are adopted as the sole policy instrument. That is, there is a need for other policy instruments such as command and control or economic instruments to ensure that organisations meet minimum standards of performance. However, voluntary approaches can make a significant contribution in situations where they provide a transitional function (for example, as a precursor to the implementation of legislation) or where they are used as a tool to assist organisations meet the goals specified in policy or regulations. While the proponents of voluntary approaches have argued that voluntary approaches offer the potential for economic efficiency, reduced administration costs, competitive advantage and innovation, there is limited evidence from the three case-studies to suggest that these benefits are achieved in practice. Soft effects such as education, placing environmental issues on the business decision-making agenda, and improving relationships between business and regulatory authorities appear to be the most important direct outcomes from successful voluntary approaches. The research indicates that, for voluntary approaches to be effective policy instruments, they should contain specific objectives and targets, clearly define the business as usual scenario, include credible monitoring and measuring processes, and be underpinned by suitable enforcement mechanisms.