Protected areas are widely held to be among the most effective means of conserving biological diversity in situ (McNeely and Miller, 1984MacKinnon et ai, 1986Leader Williams et al, 1990). A considerable amount of resources has been invested in their establishment over the last century or more, with the result that most countries have established or, at least, planned national systems of protected areas. The purpose of this paper is to examine the extent of the world's protected areas globally and regionally and to consider other options for its further strengthening and development during the twenty-first century.