The international conference Arid Lands: Today and Tomorrow drew more than 400 participants from over 3 S countries to Tucson, Arizona, for one week in October of 19 8 S. The diversity of presenters, disciplines and subject matters addressed contributed to an interesting and informative conference. The papers presented in this volume represent the efforts of scientists and other individuals who, through their various disciplines, are addressing the problems of and opportunities presented by the arid lands of the world. A committee of five scientists reviewed for substance. relevance and their contribution to the conference the 284 abstracts that were submitted. They selected 146 for presentation at the conference and of those papers presented, 128 were received for inclusion in the proceedings.