The purpose of our study was to determine the frequency of cardiac ectopy during the performance of flow-volume loops. The performance of an adequate flow-volume loop entails significant shifts in intrathoracic pressure and oxyhemoglobin saturation that could heighten myocardial arrhythmogenicity and lead to increased cardiac ectopy. Forty-two male patients referred for performance of flow-volume loops were studied with an ambulatory cardiac monitor and an arterial oxyhemoglobin saturation monitor during the performance of three flow-volume loops before and after administration of an aerosolized, selective beta 2-agonist. For comparison, the 60 min prior to and after completion of the loop testing was monitored with the continuous cardiac monitor. The frequency of cardiac ectopy was determined in four patient populations delineated by the presence or absence of cardiac, pulmonary, or cardiopulmonary disease. Each group was further divided based on the occurrence of arterial oxyhemoglobin desaturation during the performance of the flow-volume loop. We found that, despite the presence or absence of underlying cardiopulmonary disease or the occurrence of oxyhemoglobin desaturation during flow-volume loop performance, the number of cardiac ectopies diminished significantly during loop performance when compared with the 60-min study period prior to testing. This is in contrast to what had been reported previously. We conclude that the flow-volume loop is safe to perform in the general population, including those individuals with an increased risk of arrhythmias such as those with cardiac or pulmonary disease.