Many factors influence the growth, development, and final yields of corn and soybean. Of all these factors, suspected or actual herbicide injury may cause the greatest emotional response for a grower. Herbicide injury may also ultimately involve a large number people besides the grower, potentially including the consultant, agronomist, custom applicator, and chemical representatives. We developed a user-friendly, internet-based herbicide injury diagnostic key as a useful tool to aid in the diagnosis of herbicide injury. The diagnostic key can be found at http://ipcm.wisc.edu/uw_weeds/extension/herbinjury.htm.