Data from 10-day sediment toxicity tests of bed sediments from the Eighteenmile Creek Area of Concern and Oak Orchard Creek (nearby reference stream), Niagara and Orleans County, New York, respectively. Specifically, the data was used to compare the survival and growth of two macroinvertebrate species in sediments from study sites and laboratory controls. Results are from 10-day sediment exposures of two test species, Chironomus dilutus and Hyalella azteca. Sediment samples were collected from five sites on each stream. Bed-sediments were collected from depositional areas using a petite Ponar (0.03 square meter) dredge. At each site, approximately five grabs were composited into a bucket, mixed, and a 4-liter (L) subsample was stored in a polyethylene container. Sediment toxicity testing were then conducted by a contract laboratory to quantify toxicity with the dipteran, Chironomus dilutus, and the amphipod, Hyalella azteca, during 10-day survival and growth bioassays following USEPA test methods 100.2 and 100.1, respectively. U.S. Environmental Protection Agency, 2000, Methods for measuring the toxicity and bioaccumulation of sediment associated contaminants with freshwater invertebrates. Second edition: U.S. Environmental Protection Agency, Office of Research and Development EPA 600/R-99/064. This spreadsheet contains 13 columns. The first 7 columns describe the sample collection information, the remaining 6 columns provide the survival and growth results of two test species used in sediment toxicity tests. The data include the stream name, site ID, latitude and longitude, replicate number, and site type. Six columns of results from 10-day sediment exposures of two test species, Chironomus dilutus and Hyalella azteca. The following endpoints were measured for each species following the 10-day exposure: number of surviving organisms, percentage of organisms surviving (hereafter survival), and average ash-free dry weight of the surviving organisms (hereafter growth).