Fifty-one stations on the DesPlaines River and tributaries were sampled for water and sediment quality, macroinvertebrates, fish and habitat from the spring of 1983 through fall of 1984. From these data, environmental quality was evaluated utilizing various indices including water quality (WQI), macroinvertebrates (MBI), fish (AIBI) and habitat (PIBI). Individual stations were rated for degree of support of aquatic life and classified according to the Biological Stream Classification (BSC) system used for Illinois streams. Mean index values indicated poor to good environmental conditions providing partial/moderate aquatic life use at 27 of 51 stations (53%). Mean index values were 48.8 (poor) for water, 6.4 (fair-good) for macroinvertebrates, 27 (poor) for fish and 40 (fair-good) for habitat. According to the Biological Stream Classification system, 52.9% of the stations were classified as D (limited aquatic resource), 21.6% as C (moderate aquatic resource), 19.6% as E (restricted aquatic resource), 5.9% as B (highly valued aquatic resource) and 0% as A (unique aquatic resource).