The Great Lakes biota has been studied for approximately 100 years. Early investigators focused primarily on taxonomy and natural history. Building on these pioneering efforts, a comparatively large number of individuals are currently engaged in a wide array of biological investigations. Many aspects of descriptive ecology (e.g., floral and faunal composition, spatial and temporal distribution, life cycles, etc.) have been studied. Now that we are beginning to address problems in dynamic ecology (e.g., physicochemical and biological interactions, trophic interrelationships, community structure, ecosystem modeling, etc.), it is desirable to review and summarize our knowledge of the composition of the Great Lakes flora and fauna through the compilation of annotated checklists.