This report presents the basic data that were collected by the U.S. Geological Survey during a study of the chemical quality of water in Flaming Gorge Reservoir. An interpretive report will follow. The basic data were collected from the reservoir during six sampling runs between October 1970 and September 1972. The reservoir was sampled for chemical analyses at 17 sites. Chemical and physical data were measured in situ at 34 sites. The sites are shown in figure 1 and the data are listed in tables 1 and 3-6.