Sixteen stations on Rock River tributaries were sampled for water, sediment, fish populations, and habitat quality in 1985. From these data, environmental quality was summarized utilizing various indices including water quality (WQI), fish (AIBI), and habitat (PIBI). Individual stations were evaluated for degree of support of aquatic life and classified according to the biological stream classification system used for Illinois streams. All mean index values indicated good environmental conditions providing full aquatic life use at ten of 16 stations (62%). Mean index values were 26.1 (WQI) for water, 43 (AIBI) for fish and 41 (PIBI) for habitat. According to the biological stream classification system, 56% of the stations were classified as B (highly valued aquatic resources) and 44% as C (moderate aquatic resources).