As a part of the Integrated Atmospheric Deposition Network, atmospheric organochlorine pesticide concentra tions were measured in both the gas and particle phases at seven sites near the Great Lakes. Much higher organochlorine pesticide concentrations were found in the gas phase compared to that in the particle phase. Long-term decreasing trends were observed for most pesticides in both phases. Two different seasonal trends were observed in the particle phase: (a) in-use pesticides, such as endosulfan, showed higher concentrations in the summer, a time corresponding to their agriculture use, and (b) restricted organochlorine pesticides, such as lindane, showed higher particle-phase concentrations in the winter, presumably due to their enhanced partitioning from the gas phase to particles. Generally, Chicago had the highest concentrations of chlordanes, dieldrin, and DDT, suggesting that urban areas could be sources of these compounds to atmosphere. Point Petre had the highest concentrations of endosulfan, likely due to its agricultural application in Southern Ontario.