Many cardiac patients complain that they are unable to lie on their left side, or less often on their right side, because of shortness of breath, unusual awareness of the heart beat, palpitation, or pain. Wood and Wolferth1 called attention to this fact in 1937 and studied 52 cardiac patients who exhibited a distinct preference for lying on one side. They offered the term trepopnea (Greek "trepein" to turn + "pnoia" breath—Dorland's Illustrated Medical Dictionary, 23rd edition), at the suggestion of Dr. Richard A. Kern, to express this complaint. Although physicians caring for an adult population frequently encounter complaints consistent with trepopnea, the recognition of such a preference in the pediatric group is rare. In a cardiology practice that includes a large number of pediatric patients, I have recently observed trepopnea for the first time. Its manifestation and clinical implications will be discussed in this brief report.