Objetives: 100 mcg intrathecal morphine (ITM) for hip arthroplasty provides adequate functional recovery and reduces associated complications but is not exempt from opioid-related adverse effects. We evaluate efficacy of a reduced dose of ITM (80 mcg) in terms of anesthetic quality, postoperative analgesia, complication rates and early recovery. Methods: Case-control study. Patients under hip arthroplasty were treated on a specific protocol, using neuraxial anesthesia with hyperbaric bupivacaine 10.5-13.5 mg plus 80 mcg ITM versus controls with 100 mcg ITM. Demographic variables, intra and perioperative course were extracted from medical records. Pain severity and morphine associated complications were blindly assessed at regular intervals postoperatively. p < 0.01 were considered significant. Results: 82 patients were analyzed. Mean age was 64.21 years, 62.20% women and 70.73% ASA-2. Main endoprosthesis indication was arthrosis (58.53%). No statistically significant differences in demographic and operative data were found between groups, including surgical time, ambulation time, length of stay, and patient satisfaction for pain management. Mean VAS for pain during first 24 hours was 0.24 for the low ITM group and 0.22 for control. Rescue intravenous morphine was the same between groups. Compared to 80 mcg ITM, 100 mcg showed trends for higher complication rates for respiratory depression (OR 2.58, CI 95% 0.45-14.54, p = 0.28), nausea without vomiting (OR 1.82, CI 95% 0.82-4.01, p = 0.13), urinary retention (OR 2.02, CI 95% 0.88-4.61, p = 0.09) and significantly higher rates of pruritus (OR 3.55, CI 95% 1.61-7.82, p < 0.01). Conclusions: 80 mcg ITM during spinal anesthesia for hip arthroplasty provided comparable postoperative analgesia and lower incidence of opioid-related adverse effects.