OBJECTIVE The objective of the report is to describe a case of asystole lasting for 18 s, which developed after a subconvulsive stimulus during electroconvulsive therapy (ECT) in a patient without pre-existing cardiovascular abnormality. A brief review of the relevant literature is also provided. METHODS The patient was a 65-year-old Chinese man with a 2-year history of depression and good past medical health. Earlier he had responded well to a course of ECT without adverse effects. This time he presented with low mood, anhedonia, poor appetite and constipation. He did not respond to adequate trials with several antidepressant medications. When a subconvulsive stimulus was administered to determine the seizure threshold, no seizure activity was detected. However, immediately after the stimulus the patient developed an 18-s asystole, followed by bradycardia of 40 beats per minute for 10 s. The bradycardia resolved spontaneously before therapeutic intervention was effected. METHODS Intravenous atropine was employed as premedication and suprathreshold stimulus was used in further ECT sessions. RESULTS Asystole did not recur in the subsequent six ECT sessions. CONCLUSIONS When proper precautions are taken, asystole does not necessitate the suspension of further ECT sessions but intravenous atropine should be considered as premedication in such cases. Inducing anaesthesia with methohexital, avoiding excessive amounts of succinylcholine and employing suprathreshold stimulus and unilateral electrode placement may further lessen the likelihood of asystole in susceptible cases.