Seedlings of Siberian elm (Ulmus pumila L.) readily invade grasslands of the Southern Plains and are a serious economic problem. Siberian elm was not susceptible to foliage or basal sprays of phenoxy herbicides applied during 3 successive years. Individual trees were killed easily by 1 g (ai) per inch of trunk diameter of 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) or 3-phenyl-1,1-dimethylurea (fenuron) applied in a ring around the tree. However, the dense population and rapidity of reinvasion make this treatment too expensive.