• The identification of patients at high risk for the development of tardive dyskinesia (TD) is a major problem in psychopharmacology. We found a possible relationship between the subcortical B-mitten EEG pattern and TD. Twenty-one TD patients were matched on a number of relevant variables with 21 patients without TD. Ninety-five percent of the TD patients had mittens, compared to 33.3% of controls. The results suggest that the mitten dysrhythmia may be a risk factor for the development of TD. Additional findings suggest that among TD patients, mittens are differentially more frequent in younger (93.1%) as opposed to older (0.0%) subjects.