In a population of 425 individuals with Down's syndrome, 5 persons (1.2%) were identified as having Tourette's disorder. The lack of interrelationship between Down's syndrome and Tourette's disorder argues against an atypical Tourette's disorder. Diagnoses of tardive Tourette's disorder were based on absence of family history of Tourette's, late onset, and previous treatment with neuroleptic/psychostimulant medication. (Author/DB)