The U.S. Geological Survey (USGS) in cooperation with the Miami Conservancy District, Dayton, Ohio, in 2019 and 2020 collected and analyzed groundwater samples to describe concentrations of per- and polyfluoroalkyl substances (PFAS) in the Great Miami buried-valley aquifer (GM-BVA) of southwestern Ohio. Data in this release include results from PFAS analysis of groundwater samples from 23 wells from parts of the GM-BVA in Butler, Champaign, Clark, Greene, Hamilton, Miami, Montgomery, Shelby and Warren Counties within the Great Miami River, Little Miami River and Whitewater River Basins. The 23 wells used for PFAS sampling were identified and sampled previously by the USGS National Water-Quality Assessment Program to assess the occurrence of a variety of inorganic and organic contaminants in the GM-BVA. To understand the comparability of PFAS analytical results generated through different adaptations of the EPA 537.1 method, groundwater samples were collected by this study and analyzed at a contract laboratory using one proprietary adaptation (method 1; Bureau Veritas, Mississauga, Ontario, Canada) and were collected from the same wells and analyzed at a different contract laboratory by a slightly different proprietary adaptation (method 2; SGS North America Inc., Orlando, Florida).