鈥� Available assessment methods for tardive dyskinesia were reviewed under three headings: instrumentation, frequency counts, and rating scales. The more objective methods have better reliability but less certain validity, while for the clinical assessment techniques the converse tends to be true. The optimal assessment method for a given study depends on the research question asked. For most studies, the combination of one of the objective techniques with a rating method may be ideal. Research on prevalence and etiological factors would benefit from one of the multi-item rating scales, while in treatment studies a global scale may be necessary. Videotapes are invaluable for educational purposes and for training raters.