The Don River watershed is located within Canada's most highly urbanized area--metropolitan Toronto. Many residential and commercial uses, including alterations to the river's course with bridges, have had a significant impact on the Don's fauna and flora. Pollutants have degraded the river's water quality, a situation exacerbated by the construction of the Don Valley Parkway, which turned the lower Don River into a major transportation corridor. This article describes the investigation conducted by biology students from Ontario Science Centre Science School on the main Don River tributaries using macroinvertebrates as indicators. As concerned investigators, they brought awareness to the community and especially to the nonbiology students who volunteered with the study. The macroinvertebrates assessment is based on the varied sensitivity to pollution among the species. All students helped collect data, and some volunteered to pursue library research. These amateur biologists collaborated in different areas of the project. Some pursued the environmental impact of the industries along the river and the highway. Others researched benthic macroinvertebrate life cycles. This community project has raised the awareness of pollution and how stream fauna can be used to assess pollution levels.