Transesophageal echocardiography with the use of pediatric probes is nowadays commonly performed. However, in small children, insertion of a probe with a diameter of 7 mm may be traumatic or even impossible. We therefore tested a 17-element, 4 mm transverse plane probe in 136 pediatric patients, mainly in the operation room, catheterization laboratory, or the intensive care unit, and in three healthy adult volunteers. This probe was easy to insert, particularly during emergency situations, did not cause any complication in any patient, and provided satisfactory information despite the low number of elements. The use of a 4 mm transesophageal probe can improve the management of neonates with congenital heart disease in the operating room or the neonatal intensive care unit.