In July, 1987 the Illinois Environmental Protection Agency (IEPA) and the Illinois Department of Conservation (IDOC) participated in a cooperative survey of the Mackinaw River, a sixth order tributary to the Illinois River, to evaluate the aquatic resources of the basin. Water and sediment chemistry, macroinvertebrates, fish and instream habitat data were sampled at twenty-two stations to assess biotic potential and assign use support ratings. Site selection included two stations which are part of the IEPA stream monitoring network (AWQMN) and historical IDOC fish monitoring sites. Data was analyzed using a variety of indices: water quality (WQI), macroinvertebrates (MBI), fish (AIBI) and habitat (PIBI). Mean index values for the Mackinaw River basin were 42.9 WQI, 5.3 MBI, 48.7 AIBI and 43.6 PIBI. These values indicated minor water quality problems primarily due to phosphorus and total suspended solids. They also indicated that most of the streams sampled were capable of supporting a diverse macroinvertebrate community comprised of intolerant organisms and a highly valued fishery resource.