To the Editor: Tardive dyskinesia (TD) is very well known side effect of typical antipsychotics. However, it is rarely reported with anti-cancer medication. We report a first journal case of TD in 48-year-old-woman who has been on anastrozole for the last 3 years for carcinoma of the breast. We postulate that the central aromatase inhibition of anastrozole leads the compensatory up-regulation of postsynaptic receptors, supporting the dopamine supersensitivity hypothesis of TD. Oncologists and neurologists should be aware of this side effect, which may occur with long-term use. We also suggest the inclusion of the Abnormal Involuntary Movement Scale to assess TD in all prospective clinical trials of anastrozole.