To investigate the morbidity after coronary artery bypass grafting, one hundred and seventy-eight patients were retrospectively studied with a minimum follow-up period of one year. Although there was no difference in the incidence and distribution of pain in hospital, seventy percent of patients who had an internal mammary artery used as one of the bypass conduits experienced chest wound pain after discharge from hospital compared to 51.7% of patients who had vein grafts alone (P less than 0.05). Twenty-three percent of patients who had left internal mammary arteries harvested experienced chronic left-sided chest wall pain compared to 4.5% of patients who had vein grafts only (P less than 0.005). The possible factors responsible are discussed and a review made of the complications which may result from using the internal mammary artery in coronary artery surgery.