A data release containing information on benthic macroinvertebrate communities and sediment toxicity in the Eighteenmile Creek Area of Concern and a nearby reference area at Oak Orchard Creek. Bed sediments were collected during summer 2021 at 8 sites on Eighteenmile Creek and at 6 sites on Oak Orchard Creek using a petite Ponar dredge for macroinvertebrate identification and sediment toxicity testing. Macroinvertebrates were identified to the lowest practical taxonomic resolution and used to calculate metrics of biological integrity following standard New York State Department of Environmental Conservation procedures. 10-day sediment toxicity tests were conducted using two test species, Chironomus dilutus and Hyalella azteca, following USEPA test methods 100.2 and 100.1, respectively. In situ habitat measurements and sediment samples for determination of grain size distribution and total organic carbon concentration were also taken at the time of sample collection at all sites. The data release has four separate tables: one containing site locations and habitat information, one containing the results of sediment toxicity tests, one containing macroinvertebrate identifications, and one containing standard New York State Department of Environmental Conservation metrics of macroinvertebrate community integrity calculated from the macroinvertebrate identifications.