This research focused on investigating the impacts of two cattle feedlots in the Chinook region of Alberta on the microbiological quality of air within the sites and in their immediate areas of impacts. A total of 5400 air samples were collected during the spring and fall of 1999 and 2000, from locations upwind, within the feedlots and downwind of the feedlot, and analysed for microbiological parameters used as indicators of air pollution. Odour intensities were also rated on-site by technicians involved in the sampling at the sites. Thirty-six grab samples were collected and sent for olfactometric odour analysis. The correlation between odour and microbial populations were also investigated and the levels of microbial indicators were compared to standards compared to the standard threshold limit values for livestock facilities. Analyses of data show that though the microbial populations in the feedlot were generally at elevated level when compared with upwind air quality, the levels were generally within the standard threshold limit value set for livestock facilities. All bacterial populations returned to upwind values between 0.5 and 1 km downwind of the facilities. Quantitatively, other indicator groups that are of health concern (fecal coliform, and actinomycetes) were similar in the feedlots to un-intercepted upwind air quality. Fungal (molds and yeast) populations were generally lower within the feedlots than in air samples upwind and downwind of the facilities. Populations of gram negative bacteria, fecal coliforms and thermophylic actinomycetes were either not detected or negligible in the sample to obtain statistically valid results. Total heterotrophic bacteria population showed a high correlation (r=0.80) with on-site odour intensities that were recorded at the time of sampling. The correlations between olfactometric odour intensities and odour intensities recorded on site were very low (r<0.5). Elevated microbial populations were observed to be associated with dust due to vehicle movements and other activities in the feedlots. Microbiologically, air quality downwind from the feedlots returned to upwind levels at between 0.5 km from the feedlots, and the levels of microbial populations were generally below the standard threshold limit values.