There are currently 521 unique cases (species x site of action) of herbicide resistant weeds globally, with 263 species (152 dicots and 111 monocots). Weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 164 different herbicides. Herbicide resistant weeds have been reported in 94 crops in 71 countries. The website has 3025 registered users and 642 weed scientists have contributed new cases of herbicide resistant weeds. View Recent Additions, Site of Action Summary, or the Herbicide Classification System.