A case of anticholinergic psychossis in a 17-year-old male following suspected ingestion of an unknown amount of benztropine mesylate is discussed. The borderline mentally retarded patient exhibited acute psychosis and physical signs common to anticholinergic and amphetamine intoxications such as mydriasis, tachycardia and hypertension. Intramuscular chlorpromazine hydrochloride and oral haloperidol were administered to sedate the patient. The differential diagnosis of anticholinergic intoxication was based on the patient's physical and mental symptoms, the short duration of the psychosis and a negative urine assay for amphetamine. The neuropsychiatric signs of and treatment for anticholinergic psychosis are discussed. Physostigmine salicylate is the drug of choice for reversing the signs and symptoms of anticholinergic poisoning. Benzodiazepines may be used if sedation is indicated, but use of phenothiazines for this purpose should be avoided.