Poor aggregation reduces infiltration, increases runoff, and causes serious water erosion in many areas. These factors (especially reduced infiltration in the semi-arid prairie) influence soil/crop quality. Aggregate stability was assessed on cultivated and uncultivated fields in southern Saskatchewan. Three different landscape positions in three parent material types were evaluated. The relative importance of some of the mechanisms causing soil aggregate breakdown in the cultivated sites were also investigated. It was found that different mechanisms were important at different sites, however, landscape position had no influence. This paper will focus on the factors affecting soil aggregation at the three sites studied.