Published by the American Geophysical Union as part of the Special Publications Series. This report presents the results of an inventory of representative and experimental watershed studies conducted by Federal and State agencies and universities in connection with development of water resources in the United States. Most of the studies described in this report currently are under investigation; a few of the studies have been terminated. Many other studies terminated by the various agencies are not included in this report. In order to avoid misinterpretation by the many people reporting this information, the following distinction between representative and experimental watersheds was made for guidance purposes: (a) An experimental watershed is one that has been chosen and instrumented for study of hydrologic phenomena; (b) a representative watershed is one that has been chosen and instrumented to represent a broad area, in lieu of making measurements on all watersheds. Studies using experimental watersheds imply a search for principles, relationships, and factors for prediction schemes; studies using representative watersheds imply that data are transferred quite directly to other watersheds where similar measurements are not available.