Benthic samples were taken from 286 stations covering all areas of Lake Michigan in 1975 as part of a sedimentological survey of the Great Lakes. From these samples a total of twenty-seven oligochaete species were identified. Stylodrilus heringianus was the most abundant species in the lake and densities were inversely related to organic content of the sediments. Tubificids exhibited localized concentrations in Green Bay and in the northern and southern basins. Comparison of several methods using oligochaete data to assess water quality showed similar patterns, indicating that Southern Green Bay and parts of the southern and northern basins of the lake are organically enriched environments. With the exception of the northern basin, which had not previously been surveyed, these conclusions are consistent with earlier regional oligochaete surveys of the lake. The northern basin of Lake Michigan warrants further study to generate and test hypotheses concerning tubificid species distributions observed there.