Abstract: AIM To compare the effect of patient-controlled morphine analgesia (PCA) with intermittent intramuscular analgesia (IM) on the stress response in patients after off-pump coronary artery bypass grafting (OPCABG). METHODS Thirty patients were randomly allocated to PCA group (nⅠ=15) and IM group (nⅡ=15). The patients in groupⅠ received morphine with bolus dose of 2 mg, continued dose of 1mg/h and lock-out time of 15 min while the patients in groupⅡ received morphine 10 mg I.M. per 4 h. The VAS scores of the pain (rest and cough) were observed at the extubation, 12 h, 24 h, 36 h and 48 h after operation and the levels of blood glucose, plasma insulin and cortical were measured before anesthesia, at 90 min after incision and 24 h and 48 h after operation. RESULTS Pain scores of GroupⅠ were significantly lower than those of GroupⅡ at the 12 h, 24 h, 36 h and 48 h after operation (P<0.01). The levels of plasma insulin were markedly elevated at the 24 h and 48 h after operation (P<0.05), no significant difference was observed between the two groups. The levels of blood glucose and cortical of the two groups were raised at 90 min after incision (P<0.05). In groupⅠ, they were restored to the level before anesthesia at the 48 h after operation and in group Ⅱ, they kept at the high levels till 48h after operation. The levels of blood glucose and cortical in groupⅠwere significantly lower than those in GroupⅡ after operation (P<0.05). CONCLUSION Intravenous PCA more effectively alleviates the postoperative pain and stress response than intermittent intramuscular analgesia in patients after OPCABG.