The Canadian Historical Temperature Database (CHTD) was developed to meet the need for detailed individual station datasets and to produce an improved historical climate change database. It contains datasets of monthly mean maximum and minimum temperatures for 210 Canadian stations. Stations were selected on the basis of length of record, data completeness, and spatial distribution across the country. Records from separate stations were sometimes joined to temporally extend their series backward. Missing data gaps were estimated using highly correlated neighbour stations. Relative homogeneity was assessed using a Canadian developed technique based on regression models. Nonclimatic steps resulting from station or site relocations were identified and quantified. Data adjustments were performed for large steps (greater than 0.6°C) with or without metadata and for medium steps (0.4–0.6°C) with support. A bias in minimum temperatures was also identified and adjusted at principal stations located in eastern Canada. The bias results from a change in observing procedure in 1961 throughout the country, and it typically produces a decreasing step of about 0.6–0.8°C in the annual series in the eastern part of the country. Although also detectable in western Canada, it appears to be small there and no bias adjustments were performed in the western part of the country. Large temporal and spatial differences in data availability exist between areas north and south of 60°N latitude making national analyses possible for only the latest 50 years of data. Spatial presentation of the linear trends before and after adjustments shows overall improvement to the regional and national trends in terms of spatial consistency. The CHTD contains the best available monthly temperature data in Canada and these datasets are now available to the climate change research community. Copyright © 1999 Royal Meteorological Society