BACKGROUND: Generally, for patients with cancer, chronic disease, burn injury or pediatric patients to whom oral medication is difficult or whose vessels are fragile, it is difficult to inject analgesics parenterally. To know the effect of subcutaneous infusion which would be directly used by patients themselves or their care givers, we compared subcutaneous patient-controlled analgesia (SQ PCA) with intravenous patient-controlled analgesia (IV PCA) morphine for acute postoperative pain. METHODS: We undertook a study to prospective, randomized, controlled patients (n = 30) undergoing elective total hysterectomy to compare SQ PCA with IV PCA morphine for postoperative pain control. We prepared a 5 mg/ml solution of morphine for the SQ PCA group (n = 15) and a 1 mg/ml solution of morphine for the IV PCA group (n = 15). The regimen of morphine was a basal rate 20 microgram/kg/h, 1 mg bolus, 10 min lockout interval, 1 hour limit of 8 mg. We evaluated the VAS score at rest and at coughing after postoperative 6, 12, 18, 24, 30, 36, 42 and 48 hours, 6 hourly doses of morphine, total requirement of infused morphine for 48 hours and delivery to demand ratio. Side effects and satisfactory score were checked too. RESULTS: The Visual analogue scale (VAS) pain score at rest and with coughing, the 6 hourly doses of morphine, the total requirement of infused morphine for 48 hours, the delivery to demand ratio, side effects and the satisfactory score were not significantly different in the two groups (P<0.05). CONCLUSION: Thus SQ PCA morphine represents a clinically acceptable alternative to IV PCA in the treatment of postoperative pain control.