Two U.S. long-term air quality indices, the National Air Quality Index, NAQI, and the Extreme Value Index, EVI, are calculated for 27 cities in Canada, for the period 1973 to 1976. The results indicate that air quality varies considerably in space and time and that no clear trends can be discerned. Total suspended particulate matter, ozone, and sulphur dioxide are the air pollutants most commonly found to exceed the air quality standards in the residential, commercial, and industrial areas of the 27 cities studied.