One hundred and three patients ASA grades I–II, 16–80 years of age scheduled for arthroscopic meniscectomy were prospectively studied, and randomly allocated to one of four groups: group 1 (n=25): 0.25% bupivacaine (50 mg) intra-articular (IA), group 2 (n=27): 1 mg of 0.1% preservative free morphine chloride in saline, group 3 (n=26): 1 mg of 0.1% preservative free morphine chloride in 0.25% bupivacaine and group 4 (n=25): normal saline (0.9%). The volume given was always 20 mL. Ketorolac [Toradol®, 30 mg intramuscularly (i.m.)] was used as rescue medication; analgesia was assessed using a visual analogue scale (VAS), a verbal rating scale (VRS), supplemental analgesic consumption post-operatively (SAC) and the presence of side effects. Verbal rating scale and visual analogue scale scores showed better pain control in group 1, 20 min after surgery, and in groups 1 and 2 at 4 h and 10 h as well as in the global VAS. In multi-factorial analysis no significant differences among groups or side effects was found. pH analysis of the substances used showed no alterations in the basal pH range. The analgesic efficacy of 20 mL of bupivacaine 0.25% is similar to that of 1 mg of morphine in 20 mL of saline 0.9%. The morphine–bupivacaine mixture was no more efficacious than bupivacaine or morphine alone.