There are two types of water-resources activities of the U.S. Geological Survey in Wyoming: collection of hydrologic data, and water-resources-appraisal projects. During Fiscal Years 1988 and 1989, the work was done in cooperation with 10 State agencies, 5 counties, 3 cities, 2 towns, 1 irrigation district, 2 Indian Tribes, and 8 Federal agencies. Lists and location maps are included for 180 streamflow stations, 16 reservoir stations, 120 surface-water-quality stations, 15 sediment stations, 88 groundwater-level observation wells, and 73 groundwater quality sites, which were in operation during Fiscal Year 1988 and (or) Fiscal Year 1989. During Fiscal Years 1987 and 1988, 17 streamflow stations, 13 surface-water-quality stations, 14 sediment stations, and 7 groundwater level observation wells were discontinued. During Fiscal year 1988 and through the first quarter of Fiscal Year 1989, 21 streamflow stations, 15 surface-water-quality stations, and 3 sediment stations were established or reactivated. Descriptions, location maps, and progress statements are given for 4 data collection projects and 27 water resources-appraisal projects that were active during Fiscal Year 1988 and (or) Fiscal Year 1989. Eleven projects were completed during Fiscal Year 1988 or 1989 and 10 projects that were completed except for the project reports. Also included is a bibliography of reports by U.S. Geological Survey authors about the water resources of Wyoming. (USGS)