We have compared cardiovascular responses to induction of anaesthesia and to tracheal intubation after propofol 2.5 mg kg-1 and pancuronium 0.1 mg kg-1 in 10 diabetic and 10 matched, non-diabetic (control) ASA I patients. Anaesthesia was maintained with 0.8% enflurane and 50% nitrous oxide in oxygen, with assisted ventilation. The trachea was intubated 3 min after induction of anaesthesia. All 10 diabetic patients (but no controls) had abnormal autonomic function when tested on the day before surgery. There was no difference between the two groups in the pre-induction cardiovascular state. Mean arterial pressure and vascular resistance decreased after induction in each group (P < 0.05). Heart rate increased (P < 0.01) and cardiac index was sustained in the control group, but in the diabetic group heart rate did not change and cardiac index decreased (P < 0.01). There was an earlier decrease in stroke index in the diabetic group (2 min) compared with the controls (5 min). After tracheal intubation, heart rate and cardiac index in the control group and cardiac index in the diabetic group remained unchanged. However, there was a greater increase in heart rate, mean arterial pressure and vascular resistance in the diabetic group compared with the controls after tracheal intubation (P < 0.05). The exaggerated pressor response to tracheal intubation, in the diabetic patients, may reflect autonomic dysfunction.