The authors present two cases in which Gilles de la Tourette syndrome was present in at least two family members: the first case is a mother and her son and the second an uncle and his nephew. the increasing severity of the syndrome from one generation to the next and some similar clinical features in the two cases are noted. The authors also speculate that the incidence of family cases of Tourette syndrome may be underestimated because of the painstaking efforts required to obtain this kind of history.