tU.S. castor production is limited in part due to only one labeled herbicide (trifluralin) for effective weedcontrol. Field studies were conducted in south Texas and in the Texas High Plains in 2008, 2009, 2012,and 2013 to evaluate castor tolerance and weed efficacy following the application of preemergence (PRE)herbicides. During years of little or poor rainfall, no castor injury was noted following the application ofPRE herbicides. However, when rainfall occurred soon after application of PRE herbicides, linuron dosesof 1.12 kg/ha or greater resulted in stunting of castor plants and reduced stands when compared withthe non-treated control. Acetochlor, clomazone, pendimethalin, and trifluralin consistently caused theleast injury to castor plants. However, castor bean yield in many instances was not affected by herbicideinjury. Diuron at doses of 1.12 kg/ha or greater and the combination of diuron plus linuron at 0.56 kg/ha orgreater effectively controlled (> 80%) smellmelon (Cucumis melo L. var. Dudaim Naud.) and Palmer ama-ranth (Amaranthus palmeri S. Wats), but provided inconsistent control (0–99%) of Texas millet [Urochloatexana (Buckl.) R.Webster]. Results of these studies indicated that castor tolerance to PRE applicationsof acetochlor, clomazone, and pendimethalin was excellent, thus providing the greatest opportunity forfuture use in castor production.