U.S. Geological Survey investigations of the water resources of Montana are described. Hydrologic information and knowledge of the water resources are gained and disseminated principally by programs of (1) collecting hydrologic data on a continuing basis , (2) conducting water-resources appraisals of surface and ground water, (3) conducting supportive research in hydrology and related fields, (4) disseminating water data and results of investigations to the public, (5) coordinating acquisition of water data by Federal agencies, and (6) providing technical assistance in hydrologic fields to other government agencies. The Montana district of the U.S. Geological Survey conducts its hydrologic work through a headquarters office in Helena, a subdistrict office in Billings, and field offices in Helena, Fort Peck, and Kalispell. The district employs 67 people to work on 25 funded projects that are organized under the general categories of data-collection programs, problem-oriented studies , a real appraisals, coal-related studies, research projects, and hydrologic studies and research performed under contracts to research organizations. (USGS)