The effect of 20 mL of intraarticular bupivacaine (0.25%, with or without 1:200,000 epinephrine), morphine (0.03%, with or without 1:200,000 epinephrine), or normal saline on postoperative analgesia after arthroscopic knee surgery was studied in a randomized, prospective, double-blind trial in ASA I–III outpatients receiving general anesthesia (n = 112) or regional anesthesia (n = 27 [spinal (n = 25) or epidural (n = 2)]). The visual analogue pain scores in the postanesthesia care unit and 3, 6, 12, and 24 h after surgery, time to first analgesic use, and total 24-h analgesic requirements were recorded. In those who received general anesthesia, the visual analogue scores were significantly lower in the bupivacaine group compared with both the morphine- and placebo-treated patients (P < 0.05). The time to first analgesic use was longer in both the bupivacaine and morphine groups when compared with the control group (P < 0.05). No significant differences were detected in total 24 h analgesic requirements among the groups. Patients who had received regional anesthesia had lower visual analogue scores compared with patients who had received general anesthesia irrespective of the intraarticular treatment (P < 0.05). Our results indicate that intraarticular injection of bupivacaine after arthroscopic knee surgery provides prolonged analgesia but that there is no significant prolonged analgesia provided by intraarticular morphine.