Abstract.(#br)Knowledge about the biodiversity of Canada’s vast peatlands is poor largely because peatlands have not been routinely differentiated from other types of habitats. Plants are better known than the animals. Systematic surveys of peatland plants began in the late 1800s, but did not begin in earnest until the 1950s. With the exception of a few marshes, peatlands are classified into bogs (18 forms), fens (17 forms), and swamps (21 forms). Bogs are the most widespread compared to fens and swamps. Peatlands occur throughout most of Canada but are most common in the Boreal, Subarctic, and Arctic Wetland Regions. Species richness for plants clearly separates bogs and fens. Average number of total species is greater in fens than in bogs. Species richness of herbs, fern and fern... allies, and bryophytes is greater in fens than in bogs, and it is greater in bogs for trees and lichens. Bryophytes contribute the most to species richness in bogs, while herbs are most important in fens. Bogs on the Atlantic coast appear to have greater species numbers of lichens and shrubs than bogs on the Pacific coast. Herbs likely contribute more to total species numbers in fens in eastern Canada than in western Canada. There are species of mammals, birds, herptiles, biting flies, beetles, dragon-flies, water mites, rotifers, and protozoans that are restricted to peatlands or are found in both peatlands and other habitats.