Forty-five patients who underwent anterolateral and posterolateral thoracotomy were studied to compare the relative efficacy of cryoanalgesia, epidural morphine, intrapleural analgesia, and intravenous morphine for relief of postoperative pain and prevention of deterioration in pulmonary function. Spirometry (FEV1, FVC) was performed preoperatively and postoperatively. Patients' pain was assessed using the 0 to 100 mm visual analog scale. Because intravenous morphine was used to supplement pain relief in the patients who received intrapleural analgesia and cryoanalgesia, total morphine use was compared to that administered to patients in the intravenous morphine group. Epidural morphine was found to offer better pain relief than the other treatment modalities. There were no differences in spirometric testing between the groups at any time during the study. Although the number of evaluable patients was insufficient to draw definitive conclusions, 12-week follow-up suggested a difference in the incidence of post-thoracotomy pain syndrome in patients who received cryoanalgesia. It is concluded that post-thoracotomy pain is best relieved with epidural morphine, compared to intrapleural analgesia, cryoanalgesia, and parenteral morphine. There was no change in the deterioration in spirometric tests after thoracotomy, nor was there any advantage offered by cryoanalgesia or intrapleural analgesia over intravenous morphine, with respect to pain relief.