A British pedigree multiply affected by the Gilles de la Tourette syndrome and spanning six generations is described. Of 122 members identified, 85 were individually interviewed, and 50 were diagnosed as 'cases'. 'Cases' consisted of 29 with definite or probable Gilles de la Tourette syndrome, 17 with definite or probable chronic multiple tics, and four with definite or probable obsessive-compulsive behaviour. Only eight of the 50 'cases' had consulted a doctor for their symptoms. 'Cases' and 'non-cases' could be distinguished on the basis of echo-phenomena, obsessive-compulsive features, self-injurious behaviour, and the trait score of the Leyton Obsessional Inventory, but did not differ significantly on any other psychopathological variables. The pattern of inheritance of the Gilles de la Tourette syndrome in this pedigree is consistent with autosomal dominant transmission.