The conservation of biological diversity is seen as a national and an international issue of importance to Australians. This is indicated by Australia's decision to sign the Convention on Biological Diversity. However, without significant policy change to funding levels and the types of conservation mechanisms used1 biological diversity values are likely to be conserved at a less than the socially optimal level implied by Australia,s ratification of the convention. Traditional approaches to meeting conservation targets have been via land acquisition and management by government, future approaches may need to include off-reserve conservation mechanisms that use a variety of economic instruments. This paper combines economic and geographical information system techniques to estimate the cost of expanding the NS\V protected area network to a range of target levels with on and off reserve mechanisms. An algorithm was developed to select areas to complement the existing conservation system and be representative of 124 environmental domain classifications. To ensure cost effectiveness, target representation levels were achieved by selection of areas in a priority order based on land use. Results indicate that land acquisition costs of achieving a 10% level of environmental region representation in NSW are not prohibitive, in fact they may equate to something like the purchase cost of four or five F-18 fighter jets. Acquisition costs of raising the area representation of each of the defined environmental domains to 10% is estimated at $360 million. However, ongoing setup and management costs to control threats to loss of biodiversity values represent a much stronger pull on the government purse.