In 50 male patients the relationship was assessed between preoperative factors, including personality and pain threshold, and postoperative pain and pulmonary changes. There were highly significant correlations between neuroticism scores and postoperative changes. Patients with a low neuroticism score were likely to have less pain, less impairment of pulmonary vital capacity and a lower incidence of postoperative complications. Analysis of extraversion scores was less conclusive. A high psychoticism score was associated with a high neuroticism score, but psychoticism did not otherwise affect the results. There was no significant correlation between preoperative pain threshold and postoperative factors. The analyses of the effect of the non-psychological preoperative factors on postoperative pain severity and pulmonary complications showed less significant results than those with neuroticism. Pulmonary complications were higher in those patients with pre-existing chest disease and the incidence of postoperative pain appeared lower in those patients who had received intraoperative analgesia. Close correlation was found between the postoperative subjective assessment of pain and vital capacity impairment. The patient's neuroticism score warrants greater attention in studies of postoperative pain.