We compared patient-controlled epidural analgesia (PCEA) with patient-controlled intravenous analgesia (PCIA) using pethidine or fentanyl in a randomized, double-blind crossover study of 80 patients after caesarean section. Patients received pethidine by PCEA or PCIA, or fentanyl by PCEA or PCIA, with a crossover of the route of administration at 12h. For pethidine, pain scores were lower with PCEA vs PCIA from 4 to 16h (P < 0.05). Pethidine consumption was lower with PCEA vs PCIA from 12 to 24h (P = 0.0005). Patients preferred PCEA to PCIA (P = 0.015). For fentanyl, pain scores were lower with PCEA vs PCIA at 12h (P = 0.045). Fentanyl consumption was lower with PCEA vs PCIA from 0 to 12h (P = 0.0007). Patients had similar preference for PCEA and PCIA. Pain scores and side-effects were similar between drugs. Plasma pethidine was similar between groups. Plasma fentanyl was higher with PCIA vs PCEA at 12h (P = 0.002). PCEA has advantages over PCIA and pethidine may be the preferred drug.