Methods were developed in a two year study, by which nematode data on community structure from water research areas can be interpreted to lead to an increased understanding of ecological conditions. Nematodes were quantitatively sampled at intervals from 16 sites along two streams near West Lafayette, Indiana. Both streams flowed through farmland and some forested areas, and one also flowed through a growing housing development. Of 156 species of nematodes identified, 74 species were considered to be benthic inhabitants. Numbers of each species present at each sampling date at each site were obtained. Data for physico-chemical parameters were also collected at each of the 16 sites at biweekly intervals. These data included values for nitrate, nitrite, dissolved oxygen, carbon dioxide, pH, total hardness, phosphates, and water temperature. Organic matter and relative quantities of particles of different sizes were determined for the substrate of each site. The study indicates that analysis of benthic nematode community structure can be a useful tool for evaluating disturbances to aquatic habitats. Sufficient information for analysis can be obtained from data on a few of the dominant species.