BACKGROUND Transversus abdominis plane (TAP) block is an alternative to spinal morphine for analgesia after Caesarean section but there are few data on its comparative efficacy. We compared the analgesic efficacy of the TAP block with and without spinal morphine after Caesarean section in a prospective, randomized, double-blinded placebo-controlled trial. METHODS Eighty patients were randomized to one of four groups to receive (in addition to spinal anaesthesia) either spinal morphine 100 µg (S(M)) or saline (S(S)) and a postoperative bilateral TAP block with either bupivacaine (T(LA)) 2 mg kg(-1) or saline (T(S)). RESULTS Pain on movement and early morphine consumption were lowest in groups receiving spinal morphine and was not improved by TAP block. The rank order of median pain scores on movement at 6 h was: S(M)T(LA) (20 mm)<S(M)T(S) (27.5 mm)<S(S)T(S) (51.5 mm)<S(S)T(LA) (52.0 mm) (P<0.05, highest vs lowest). The rank order of median morphine consumption at 6 h was: S(M)T(S) (4.0 mg)<S(M)T(LA) (5.0 mg)<S(S)T(LA) (8.0 mg)<S(S)T(S) (12.0 mg) and at 24 h was: S(M)T(LA) (5.0 mg)<S(M)T(S) (6.0 mg)<S(S)T(S) (9.5 mg)<S(S)T(LA) (15.0 mg) (P<0.05, highest vs lowest). Sedation scores and patient satisfaction did not differ between groups. Anti-emetic use and pruritus were highest in the S(M)T(LA) group. CONCLUSIONS Spinal morphine-but not TAP block-improved analgesia after Caesarean section. The addition of TAP block with bupivacaine 2 mg kg(-1) to spinal morphine did not further improve analgesia.