Postpartum bilateral tubal ligation (PPBTL) causes postoperative pain. We designed this study to determine the efficacy of 50 microg intrathecal morphine for analgesia after PPBTL. Sixty-five women received spinal anesthesia with 12.75 mg hyperbaric bupivacaine, 20 microg of fentanyl, and either 50 microg of morphine (morphine group) or 0.05 mL of saline (control group). Postoperative analgesia was provided with regular naproxen 500 mg and oxycodone 5 mg/acetaminophen 325 mg mixture as needed. Overall, satisfaction was higher (P=0.003) and pain was less intense at rest (P=0.008) and on movement (P <0.0001) in the morphine group. There was no significant overall difference in nausea, pruritus, or sedation scores, but vomiting occurred more frequently in the morphine group (21.4% versus 3.5%; P=0.052). In post hoc comparisons, pain at rest within the morphine group was significantly less at 4 h (P=0.006), pain on movement was significantly less at 4 h (P=0.002) and 12 h (P=0.0004), and pruritus was significantly more frequent at 12 h (P=0.002) compared with the control group. Oxycodone 5 mg/acetaminophen 325 mg mixture consumption was significantly smaller (P=0.006) and the time to first request of analgesia was significantly longer (P=0.006) in the morphine group. We conclude that the addition of 50 microg of morphine to intrathecal hyperbaric bupivacaine and fentanyl provides improved postoperative analgesia in women undergoing PPBTL.