Analysis of the families of 39 unselected children with Tourette syndrome revealed other members with tic disorders in twenty kindreds. In eight families there were 13 individuals with chronic multiple tics, usually motor, not vocal. Twelve different families contained 18 subjects with Tourette syndrome other than the index patient. In three of these families there were 6 additional individuals with chronic motor tics, forming a bridge to the first group. An autosomal dominant mode of inheritance was suggested in all cases. Tourette syndrome and chronic motor tics appear to represent conditions along a continuum and have, in many instances, a hereditary basis.