Epidural meperidine (1 mg X kg-1) was administered for relief of sternal pain to ten patients, at a mean of 24.8 hours after infusion of high dose fentanyl for cardiac surgery. Lung function, cough, pain score, somnolence, respiratory rate, PaCO2, pulse and blood pressure were studied before and for six hours after analgesic administration. Following epidural meperidine, four of ten patients were pain-free, and three had only minimal pain. Duration of analgesia was 8.8 +/- 4.9 hours. Cough score was significantly improved for five hours. Postoperatively vital capacity was approximately 40 per cent, and FEV1 was approximately 55 per cent of the preoperative value. There was no significant change in FEV1 or vital capacity, following analgesia with epidural meperidine. The somnolence score increased in seven patients. In the first two hours after epidural meperidine, three patients exhibited a fall in their respiratory rate, one had a PaCO2 greater than 45, and two of these patients had marked hypotension. These side effects are easily treated without mechanical or pharmacological support, and do not preclude the use of epidural meperidine after a high dose fentanyl anaesthetic.