This FAO Legislative Study (No. 92) offers a fresh look at the theory and practice of modern water rights, from a comparative law angle. It sheds light on a number of key features of such rights, and contrasts these to traditional forms and kinds of water rights. It teases out and discusses the relevant problematique, including in particular that elicited the sale and leasing of water rights. Finally, a stock-taking and assessment of modern water rights systems impacts are volunteered.