We report three cases of injury of the brachial plexus after coronary revascularization surgery. During the postoperative phase all patients presented plexopathy involving the left C8 and D1 roots. The symptoms were pain, paresthesia, and motor deficits. The proposed mechanisms for injury of the brachial plexus during cardiac surgery are: hyperabduction of the arm, direct traumatism produced by the needle during catheterization of the internal jugular vein, and traction and compression associated with sternal retraction. In the three patients we ruled out alterations during cannulation of the internal jugular vein and malposition of the arms. We think that in our cases the fundamental mechanism was an excessive and assymetrical opening of sternal and Favoloro's separators that were used in all cases during dissection of the left internal mammary artery. We conclude that injury of the brachial plexus can be minimized by reducing the opening of both separators and by placing Favaloro's separator in a lower position.