Identification and description of tardive dyskinesia have been hampered by the absence of systematic studies assessing the psychometric properties of existing instruments. The purpose of this study was to establish construct validation of one of these instruments, the Dyskinesia Identification System--Coldwater. Cross-sectional prevalence assessment data of 519 institutionalized mentally retarded persons were used. The 34 items of this instrument were subjected to exploratory factor analysis. A six-factor orthogonal solution was selected. Multiple regression analyses supported the established relationships of demographic variables, such as age and sex, with the tardive dyskinesia scores generated by the instrument.