Dick M, Campbell RM, Jenkins JM. C.S. Mott Children's Hospital, Ann Arbor, MI. Cathet and Cardiovas Diag. 10:507-513, 1984. To determine the thresholds for transesophageal atrial capture, as well as factors that may influence the thresholds, we measured the minimal current and pulse width required to pace the atria through transesophageal bipolar lead systems in 12 patients, ranging in age from 1 day to 19 years, during 19 episodes of reentran supraventricular tachycardia. Depending on patients' age and size several electrode catheters were used. The protocol called for 1-msec stepwise increments in pulse width. At each pulse width the current was increased by 1 mA until capture was achieved. The mean minimal pulse width and mean minimal current required for capture were 5.8 msec and 13.6 mA, repsectively. Atrial capture was achieved in 75% of atempts at a pulse width and current <= 6.5 msec and 17.5 mA respectively. No correlation between current and pulse width on the one hand and age, height, weight or body surface area on the other were detected. Likewise, neither electrode type nor existence of structural heart disease influenced the threshold required for capture. We conclude that atrial capture can be readily achieved through transesophageal electrodes and is not influenced by subject's age or size.