This chapter reviews information about how crop plants resist herbicides and how resistance is selected for in plants and surveys specific herbicide-resistant crops by chemical family. The discussion in the chapter includes HRCs derived from both traditional and biotechnological selection methodologies. Plants avoid the effects of herbicides they encounter by several different mechanisms. These mechanisms can be grouped into two categories: those that exclude the herbicide molecule from the site in the plant where they induce the toxic response and those that render the specific site of herbicide action resistant to the chemical. The chapter presents herbicide-resistant crops by the herbicide chemical family—such as, triazine, acetolactate synthatase, acetyl-CoA carboxylase, glyphosate, bromoxynil, phenoxycarboxylic acids, and glufosinate. Resistant crops are listed in the chapter regardless of whether they have been commercialized or were developed for experimental purposes only, and are provided regardless of their “success” as resistant plants.