The prevalence of dyskinesia was studied in 4 samples of elderly Chinese people in Hong Kong--a psychogeriatric clinic, a mental hospital, a geriatric day hospital and a senior citizen centre. Research Diagnostic Criteria were used to identify cases of tardive dyskinesia. The overall prevalence of spontaneous dyskinesia was 2.4% and tardive dyskinesia was 25.9%. The rate of spontaneous dyskinesia differs across the study samples and is related to nervous system conditions associated with increased age. On the other hand, the rate of dyskinesia associated with antidepressants may not be significantly different from that of spontaneous dyskinesia.