BACKGROUND: Infants presenting with anomalous left coronary artery off the pulmonary artery (ALCAPA) are generally in heart failure and often have significant mitral valve regurgitation (MR). Although establishing a dual coronary circulation is the procedure of choice, there remains controversy as to how the mitral valve is handled. METHODS: We reviewed our experience with this lesion at St. Louis Children's Hospital. Over the past 15 years, 17 infants under 18 months of age have undergone repair, with all but one being treated with reimplantation of the left coronary artery into the aorta; the other underwent the Takeuchi procedure (intrapulmonary artery baffle) and was excluded from this evaluation. The average age and weight at operation were 0.5 +/- 0.3 years and 6.1 +/- 1.9 kg, respectively. All presented with varying degrees of heart failure and 9 patients also had either moderate or severe MR. RESULTS: There was one early and no late deaths after reimplantation of the left coronary artery. The left ventricular function postrepair improved from a preoperative shortening fraction of 0.19 +/- 0.09 to 0.34 +/- 0.08 (p < 0.01). Moderate or severe MR was present in 2 patients postoperatively, and both developed significant obstruction in the left coronary artery postoperatively as well. Both underwent mitral valve repair and revascularization of the left coronary artery. CONCLUSIONS: Excellent results can be obtained in the treatment of this very high-risk group of patients. Mitral valve repair is not generally necessary at the time of the initial operation. However, should MR recur or persist late, it may herald the presence of a coexistent, significant coronary stenosis. Cardiac catheterization should be performed to assess the patency of the left coronary artery before performing mitral valve surgery.