Five 2,5-dimethyl-1-pyrrolidinecarboxanilides were effective inhibitors of the Hill reaction. However, only thecisisomers were active; thetransisomers were totally inactive. Experiments were conducted using14C-5328 (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide). A correlation existed between resistance of various plants to 5328 and their ability to metabolize it to water soluble metabolites. Velvetleaf (Abutilon theophrastiMedic.) and proso millet (Panicum miliaceumL.) seedlings were very susceptible to 5328 and were unable to metabolize it. Tall morningglory [Ipomoea purpurea(L.) Roth] seedlings were highly tolerant to 5328 and converted it completely to its metabolites. Corn (Zea maysL. ‘DeKalb variety XL-45′) seedlings which were slightly susceptible to 5328 injury were able to metabolize up to 90% of the parent compound. Corn foliage uptake of14C-5328 applied to the soil surface occurred through the adventitious roots.