Musician's dystonia is associated with significant morbidity. To assess treatment options, accurate and precise measurements of disease severity are critical. We describe current methods of quantitatively measuring musician's dystonia of the upper extremity including subjective, objective, and automated methods. The degree to which these methods satisfy rigorous measurement criteria, including their reliability, validity, responsiveness to treatment, and practicality, is examined. We report that most of these methods have not been properly evaluated. Therefore, treatment trials based on these methods are difficult to interpret.