In a double-blind, prospective study, 2 mg of intramuscular lorazepam and 5 mg of intramuscular haloperidol were equally effective in controlling aggression, agitation, and assaultive behavior. Although lorazepam and haloperidol produced an equivalent mean decrease in aggression, significantly more subjects who received lorazepam had a greater decrease in aggression ratings than haloperidol recipients; this effect was independent of sedation. Lorazepam produced significantly fewer extrapyramidal symptoms. These data support the current clinical practice of using lorazepam (alone, or in combination with a neuroleptic) for control of acute aggressive and assaultive behavior.