We have seen four cases of delayed postoperative pleuropulmonary complications associated with use of the internal mammary artery (IMA) conduit. In each case the left IMA was used as a bypass conduit to the left anterior descending (LAD) coronary artery. In two of the instances the complications were life-threatening to the patients. Each patient was left with symptomatic residual roentgenographic changes. The IMA is becoming the graft of choice for coronary artery revascularization. The potential for delayed pleuropulmonary complications associated with use of this graft is not well recognized.