Quantifying movement disorders is becoming crucially important in neurosurgery units to evaluate the efficacy of new therapeutic interventions such as deep brain stimulation. Kinematic analysis, available for more than a century, may represent an adequate solution to this problem. However, quantifying movement disorders poses a number of technical problems. To help clinicians quantify movement disorders, the authors present data recorded in patients with dystonic syndromes and explore the question of movement "normality" in these patients when they receive deep brain stimulation of the internal globus pallidus. In particular, they show that when one control group (n = 11) and a group of dystonic patients (n = 11) are compared, it is possible to detect subtle changes in the performance of a double-handed finger to nose test. These differences persist in the absence of differences in the clinical evaluation of these patients. Suggestions regarding the compromises to make and pitfalls to avoid when quantifying movement disorders are discussed.