This study was designed to evaluate the metabolic effects of intrathecal morphine in patients undergoing coronary artery surgery. Ten patients received 4 mg preservative-free morphine in 6 ml saline intrathecally before surgery and were compared with 10 patients anaesthetised in a similar manner, though without intrathecal morphine. Catecholamines, cortisol and glucose measurements were made during surgery and for 24 h post-operatively. The control group had a higher post-operative requirement for papaveretum, indicating that intrathecal morphine provided some post-operative analgesia. In the period from end of surgery to 5 h after surgery, cortisol secretion was suppressed in the intrathecal morphine group.