Cardiac action was monitored during the stimulation period of 120 consecutive electroconvulsive therapies. Electrode placement was right unilateral in 73, bitemporal in 11, and bifrontal in 36 cases. Anticholinergic premedication was routinely given. A reduction in heart rate was seen consistently with unilateral electrode placement and asystole longer than 2 seconds occurred in 63% of cases. In contrast, no asystole occurred with bifrontal electrode placement. Thus, the vagus nerve seems to be less activated during bifrontal stimulation.