Peat profiles were sampled from a raised bog and an interior fen located in the boreal James Bay Lowlands, Northern Ontario, and a cold-temperate swamp and a cold-temperate bog in the Great Lakes-St. Lawrence Lowlands, southern Ontario. An examination of the micromorphology and maceral compositions of the peats indicates that considerable differences exist between environments. The boreal bog and fen both consist predominantly of relatively unaltered textinite (commonly Sphagnum-derived), with higher liptinite contents in the fen profile attributable to the more diverse vegetation. Both the cold-temperate swamp and bog show high levels of humification at the surface, possibly partially attributable to recent climatic warming trends causing a decline in water table elevation. In all profiles, funginite was persistent, ranging from 2 to 10% of the total maceral content, indicating that aerobic conditions generally prevailed at the surface at the time of deposition. The influence of depositional environment and vegetation type on the resulting peat was born out in plots of Tissue Preservation Index vs. Gelification Index. The petrographic study also demonstrated that none of the profiles contained high ineaodetrinite/semifusinite contents comparable to those within cold-climate cratonic Permian Gondwana coals. Since the oxidation processes leading to the formation of inertinite are considered to take place at the peat stage, if the peats studied were to contain a similar maceral assemblage upon coalification, inertinite precursors may be present in the peat. The lack of petrographic similarity between the Holocene peats and the Permian coals may be related to a number of factors. The decrease in water table elevation possibly responsible for the inertinization of the Permian coals may have occurred following the cessation of peat formation, not concurrently with accumulation, and is potentially attributable to long-term factors such as climatic warming. The change in the peat-forming vegetation (from Permian Glossopteris- and Gangamopteris-dominated communities to Holocene Sphagnum and coniferous vegetation) alters the characteristics of the initial botanical starting materials, and some aspects of the ecology, particularly trophic and pH conditions, which control the post-depositional alteration of the plant materials and the resulting maceral assemblages.