Georges Gilles de la Tourette first drew attention to the psychopathology of the Gilles de la Tourette Syndrome (GTS) in 1889 when he commented on the anxieties and phobias of his patients. In this paper he acknowledged the contribution of Guinon, who in 1886 had noted that "tiquers" nearly always had associated psychiatric disorders characterised by multiple phobias, arithmomania and agoraphobia. Since that time many types of psychopathology have been documented in association with GTS, including depression, anxiety, phobic disorder, hostility and aggression. However, the exact association between these disorders and GTS remains unclear. What is becoming increasingly evident is that there is a clear and strong association between obsessional thoughts and behaviours and GTS, and this is seen both in patients with GTS and in their family members. There have now been at least twenty investigations which have reported on this association, which is evident in clinic patients, epidemiological studies and family/pedigree populations. There have also been convincing arguments for the association being genetic.