Anomalous origin of the circumflex coronary artery is extremely rare and may cause acute cardiac decompensation associated with correction of coexisting congenital malformations. We describe a 10-year-old female patient who underwent surgical repair of the aortic coarctation at 4 years of age. Six years later, she presented with chest pain during exercise. Cardiac catheterization demonstrated 25 mmHg subaortic systolic gradient and retrograde filling of the circumflex coronary artery from the left anterior descending and right coronary artery, with drainage into the right pulmonary artery. Reimplantation of the anomalous circumflex coronary artery to the aorta and resection of subaortic fibrous membrane was performed. Her postoperative course was uneventful, with complete relief of symptoms. (C) 1997 Elsevier Science B.V.