Aggressive control of pain during the immediate postoperative period after cardiac surgery with early tracheal extubation may decrease morbidity and mortality. This prospective, randomized, double-blinded, placebo-controlled clinical study examined the use of intrathecal morphine in patients undergoing cardiac surgery and its influence on early tracheal extubation and postoperative analgesic requirements. Patients were randomized to receive either 10 micrograms/kg of intrathecal morphine (n = 19) or intrathecal placebo (n = 21). Perioperative anesthetic management was standardized (intravenous (IV) fentanyl, 20 micrograms/kg, and IV midazolam, 10 mg) and included postoperative patient-controlled morphine analgesia. Of the patients who were tracheally extubated during the immediate postoperative period, the mean time from intensive care unit arrival to extubation was significantly prolonged in patients who received intrathecal morphine (10.9 h) when compared to patients who received intrathecal placebo (7.6 h). Three patients who received intrathecal morphine had extubation substantially delayed because of prolonged ventilatory depression. Although mean postoperative IV morphine use for 48 h was less in patients who received intrathecal morphine (42.8 mg) when compared to patients who received intrathecal placebo (55.0 mg), the difference between groups was not statistically significant. In conclusion, intrathecal morphine offers promise as a useful adjunct in controlling postoperative pain in patients after cardiac surgery. However, the optimal dose of intrathecal morphine in this setting, along with the optimal intraoperative baseline anesthetic that will provide significant analgesia, yet not delay extubation in the immediate postoperative period, remains to be elucidated.