Digital movement analysis (DMA) is a new instrumental approach to assessing oral tardive dyskinesia (TD) by means of digital image processing of a video signal, tracking five paper dots placed around the patient's mouth. A total of 40 schizophrenic patients, 30 with and 10 without TD, were examined twice (with a 3-month interval) with this new device. The patients were further examined with two TD rating scales: the St. Hans Rating Scale for extrapyramidal syndromes (SHRS) and the Abnormal Involuntary Movement Scale (AIMS). The schizophrenic patients accepted the instrumental assessment without any anxiety or resistance. The internal reliability of the apparatus was high, with correlation coefficients of 0.80-0.99. The DMA TD values correlated with the SHRS and AIMS scores with correlation coefficients of 0.48-0.73 indicating an acceptable, although not strong, concurrent validity. Fluctuations occurred from the first to the second examination independent of medication. For these fluctuations no correlation was found between DMA values and rating scores. Finally, the DMA device was able to detect perioral tremor as a sign of parkinsonism. It has been concluded that DMA is a useful supplement to classical TD rating, although further validity evaluation is warranted.