The biosand filter (BSF) is a promising point of use (POU) technology for water treatment; however there has been little follow-up of initial implementation to assess sustainability. The purpose of this study was to examine continued use, performance, and sustainability of previously implemented concrete BSFs in Bonao, Dominican Republic. Of 328 households visited and interviewed, 90% of BSFs were still in use after approximately 1 year since installation. Waterquality improvement, measured by fecal indicator bacteria reduction, was found to be 84–88%, which is lower than reductions in controlled laboratory studies but similar to other field assessments. In a short prospective cohort study comparing BSF to non-BSF households, odds of reported diarrheal disease in BSF households were 0.39 times the odds of reported diarrheal disease in non-BSF households. These results document high levels of sustained and effective concrete BSF use and associated improvements in water quality and health.