OBJECTIVE: The purpose of this study was to assess the long-term outcome of patients with tardive dyskinesia. METHOD: A group of 122 neuroleptic-treated Hungarian outpatients were assessed for tardive dyskinesia on the Abnormal Involuntary Movement Scale and the Tardive Dyskinesia Rating Scale by the same rater over a 10-year period. RESULTS: Sixty-three of the patients received both 5- and 10-year follow-up assessments and are the subjects of this report. The overall prevalence of tardive dyskinesia in this group changed little over time; it was 30.2% at baseline, 36.5% at 5 years, and 31.7% at 10 years. However, there were changes in the tardive dyskinesia status of individual patients; 11 patients had remissions, and 12 who did not have tardive dyskinesia at the baseline assessment had developed it by the 10-year assessment. These two subgroups did not differ significantly on demographic and drug history variables. Outcome of tardive dyskinesia was not significantly related to neuroleptic treatment or to age. CONCLUSIONS: The data of this 10-year follow-up study provide evidence for the long-term stability of tardive dyskinesia and for the feasibility of maintenance neuroleptic therapy for chronic psychotic patients who have tardive dyskinesia.