In general, the aquatic insects of freshwater wetlands have been inadequately studied despite their apparent importance in wetland habitats, especially in energy and nutrient transfer. The Biological Survey of Canada (Terrestrial Arthropods) recognized the deficiencies in knowledge of taxonomy and ecology of insect species in wetland habitats and sponsored a "Conference on the aquatic insects of peatlands and marshes" in St. Andrews, New Brunswick, on 3 October, 1984. The Conference summarized current knowledge on the systematics and ecology of aquatic insects of Canadian peatlands and marshes, the wetland habitats chosen for emphasis, and sought to identify needs for research on the structure and dynamics of aquatic insect faunas in these habitats. The proceedings of the Conference are published here. The first two papers provide background information on the habitats under consideration and the interactions among invertebrates and vertebrates in these habitats. A second group of papers considers features of the Hydracarina, Ephemeroptera, Odonata, Hemiptera, Trichoptera, Coleoptera, and Diptera in peatlands and marshes. A final paper summarizes data on the occurrence of aquatic insects in bogs, fens, and marshes, addresses broader questions related to the nature of the insect fauna, and identifies needs for further research. By making accessible systematic and ecological information on aquatic insects of Canadian peatlands and marshes, the proceedings should support and encourage further work in these habitats.