The relationship between a medication course with haloperidol (Haldol) and family history for any type of tics was examined in a survey of 196 Tourette syndrome patients. Those with no family history of tics had a high probability of success with haloperidol therapy only. A positive family history increased the likelihood of medication changes after an initial trial of the drug. Surprisingly, we found that patient gender rather than family history was more likely to predict a successful treatment outcome with haloperidol. The data suggest a complex, multifactorial pathology for Tourette syndrome that extends beyond a simple dopamine receptor dysfunction and points to the influence of patient gender on treatment outcome.