Iatrogenic chylothorax is a well-recognized complication following thoracic surgery, but is a rare occurrence after aortocoronary bypass. Only two cases have been previously reported. Two additional cases from our hospital are presented. All four male patients responded to conservative management within two weeks of initiation of treatment. Only 12 cases of chylothorax following median sternotomy have been reported (nine women and three men). Five of the nine women required surgical exploration after a course of unsuccessful management ranging from 14 to 26 days. The cause of the chylothorax was considered to be injury to lymphatic collaterals in the anterior mediastinum, which resulted in a retrograde chyle flow; the main duct remained intact. This article reviews the normal anatomy of the thoracic duct and variations of chylothorax, and describes the mechanism of injury in aortocoronary bypass, the prevention of this complication, and the results of treatment.