Western Canada (prairie provinces of Alberta, Saskatchewan, Manitoba) and Eastern Canada (primarily southwestern Ontario and Quebec) account for 88 and 12% of principal field annual crop area, respectively. Based on the proportion of total field area at prairie sites infested with herbicide-resistant (HR) weeds, it is estimated that 7.7 million ha (29% of annually cropped land in the prairies) are infested with HR weeds (eight-fold increase from 2001 to 2003), in a total field area of 9.9 million ha (37% of annually cropped land in the prairies) – over a two-fold increase. Group A/1 and/or B/2 wild oat (Avena fatua L.) are by far the most abundant and economically-damaging HR biotypes across the prairies. Numerous populations of Group B/2 wild mustard (Sinapis arvensis L.) and false cleavers (Galium spurium L.) across the prairies are also adversely impacting pulse crop (e.g., peas, lentils) production and quality. Glyphosate plus Group B/2 kochia (Kochia scoparia) is increasing rapidly across southern Alberta and Saskatchewan, primarily selected in chem-fallow or cereal-based cropped fields. In Eastern Canada (southwestern Canada), populations of glyphosate-resistant horseweed (Conyza canadensis) and giant ragweed (Ambrosia trifida) are steadily increasing (selected primarily in glyphosate-resistant corn or soybean), as are multiple-resistant populations of these species (glyphosate + Group B/2).