The U.S. Geological Survey (USGS), in cooperation with the Miami Conservancy District, Dayton, Ohio, in 2019 and 2020 investigated concentrations of per- and polyfluoroalkyl substances (PFAS) in groundwater from the Great Miami buried-valley aquifer (GM-BVA) of southwestern Ohio. The 23 wells used for sampling were identified and sampled by the USGS National Water-Quality Assessment Program to assess the occurrence of a variety of inorganic and organic contaminants in the GM-BVA. Data in this release include results from PFAS analysis of quality-control samples, including sequential replicate samples of groundwater, equipment blanks and source-solution blanks prepared before or during groundwater sampling. Wells where quality-control samples were prepared were from parts of the GM-BVA in Champaign, Clark, Miami, Montgomery, and Shelby Counties in the Great Miami River Basin. Quality-control samples were analyzed for PFAS using the same methods as for groundwater samples through different adaptations of the EPA 537.1 method at a contract laboratory using one proprietary adaptation (method 1; Bureau Veritas, Mississauga, Ontario, Canada) and at a different contract laboratory by a slightly different proprietary adaptation (method 2; SGS North America Inc., Orlando, Florida. The groundwater sampling and analyses were done to inform the public and area stakeholders about concentrations of PFAS compounds in the GM-BVA.