One of the characteristics of Roundup Ready soybeans in the first few years following their introduction was the notable absence of weeds following postemergence glyphosate applications. This applied to relatively easy to control weeds as well as those that are not well controlled by other herbicides. Some growers continue to have excellent success at weed control in Roundup Ready soybeans. However, 10 years later, several weeds have become problematic in soybeans again, and we no longer assume that all Roundup Ready soybean fields will be free of weeds at the end of the season. Weeds that currently seem to be most problematic in Roundup Ready soybeans in the eastern Corn Belt include giant ragweed, lambsquarters, horseweed (marestail or Canada fleabane), and pokeweed. There can be any number of reasons why these weeds have become more prevalent, and more difficult to control. Within the United States, populations of horseweed, common ragweed, and Palmer amaranth have developed resistance to glyphosate over the past 5 years, and we believe populations of giant ragweed are developing resistance also.