The objective of the present study was to study the heart rate, presence of arrhythmia, and changes in the ST segment of surgeons with 24-hour ambulatory electrocardiographic monitoring. Eleven surgeons of several specialties were evaluated. All surgeons had one to three operations on the day of the recording. Heart rate, presence of arrhythmia, and changes in the ST segment were determined during the following surgeons' activities: operation, sleeping, car driving, patient appointment, and eating. There was a difference in the mean heart rate among the activities (p = 0.0004). The lowest mean heart rate was registered during sleeping and the highest during operation. Two surgeons had arrhythmias: one had premature ventricular contractions (0.6% of total ventricular contractions) and the other rare premature atrial contractions (0.05% of total atrial contractions) in addition to isolated premature ventricular contractions (< 0.1% of total ventricular contractions). There was no significant difference in frequency of arrhythmia during the activities (p = 0.7150). One patient had periods of inverted T waves. It is concluded that the heart rate of surgeons increases significantly during surgery and that the occurrence of cardiac arrhythmias is not increased in surgeons with no cardiovascular disease during surgery.