A large forest fire occurred about 300 km to the northeast of the Edmonton area in early summer 1995. The forest fire produced nitrogen oxides, hydrocarbons and ozone which were transported down-wind. Continuous monitoring of O3, NO and NO2 and integrated measurements of volatile organic compounds, together with air trajectories, during the period of 1–6 June indicate that air pollutant concentrations were enhanced by the forest fire emissions. In the rural environment the influence of the forest fire on air quality could be easily detected; significantly higher NO2 and O3 concentrations were observed when air came from the direction of the forest fire area. Hourly NO2 and O3 concentration were 50–150% higher than the seasonal median values. The influence of the forest fire on air quality was also noticeable in the urban center even though local emissions are much higher than in the rural area. Maximum hourly ozone concentrations at the urban air quality monitoring stations in Edmonton on 4 June 1995 were above the 82 ppbv national and provincial air quality objectives.