Among 421 patients undergoing coronary artery bypass graft surgery, 55 (13%) developed 63 new peripheral nervous system (PNS) complications postoperatively. Most common was a brachial radiculoplexopathy, which occurred in 23 patients. Of these, 21 involved lower trunk or medial cord fibers. In 17 there was a correlation between the site of jugular vein cannulation and the side affected, suggesting that needle trauma played a role. Stretching from chest wall retraction may have caused some cases. Other deficits included 13 saphenous, 8 common peroneal, and 5 ulnar mononeuropathies. Six patients had persistent singultus, suggesting phrenic nerve involvement. Unilateral vocal cord paralysis was found in 5. An isolated partial Horner syndrome and a facial neuropathy were also identified. Males were more likely to develop PNS complications. Hypothermia during surgery was associated with increased risk. Most PNS deficits were transient, and lasting disability was rare.