Dopa-responsive dystonia, an autosomal-dominant disorder caused by mutations in the guanosine triphosphate (GTP)-cyclohydrolase I gene, is characterized by severe striatal dopamine depletion. Tardive dyskinesia, on the other hand, has often been associated with striatal dopamine overactivity. This article reports on a 44-year-old man with dopa-responsive dystonia who developed tardive dyskinesia on long-term haloperidol therapy. Nigrostriatal dopamine deficiency may be necessary for the development of tardive dyskinesia.