Respiratory dyskinesia is characterised by irregularity in rate, rhythm and depth of breathing. This study reports on the clinical features of 11 patients with respiratory dyskinesia identified from a mental hospital in Hong Kong, together with the results of the 24-hour polygraphic recording of seven patients. Virtually all patients with respiratory dyskinesia had tardive dyskinesia. However, the condition was missed or misdiagnosed in all cases by the case psychiatrists. The respiratory irregularity persisted for most of the day and only disappeared when patients took a prolonged rest or fell asleep. A standardised clinical examination for respiratory dyskinesia is proposed.