Eighteen private well users in North Carolina were recruited to test the perfor-mance of under-sink, activated carbon block water filters to remove per- andpolyfluoroalkyl substances (PFAS). Monthly sampling was conducted for8 months. Filters were certified for removal of perfluorooctanoic acid andperfluorooctanesulfonic acid under NSF International certification P473, but not foradditional short-chain perfluoroalkyl acids or perfluoroalkyl ether acids (PFEAs)evaluated in this study. Out of 47 targetedanalytes, 17 PFAS were detected in filterinfluent samples (influentPPFAS 4.7–131 ng/L). Mixed-effects Tobit regressionmodels showed that the filters effectively removed 97%–99% of all influent PFAS,including short-chain PFEAs, for the entire manufacturer-recommended lifetime ofthe device. The prevalence of PFAS above the minimum reporting limits wasreduced by 99.5%, and the prevalence ofany PFAS above the method detectionlimits was reduced by 92%. The results provide increased confidence in NSFP473-certified filters for the removal of PFAS from private well water