A single dose block randomised double-blind study comparing intramuscular ketorolac, 50 mg of pethidine and 100 mg pethidine was carried out in multiparous women. Pain intensity and sedation effect were recorded at inclusion to the study, half hourly for the first 2 h, then hourly until 6 h after delivery. Maternal and neonatal side effects were noted including the Apgar scores and the baby's requirements for resuscitation. All three treatments are relatively ineffective in relieving labour pain. There was no difference in the analgesic efficacy between the two doses of pethidine but both doses of pethidine were statistically more effective compared with ketorolac. There was no difference in the retrospective assessment of the three groups or when comparison was made with the previous labour. A similar number of patients required further analgesia in each group. In all three groups, no adverse effect occurred in the mother or fetus. Maternal sedation and fetal depression were statistically less in the ketorolac group. Although ketorolac had inferior analgesic effect, its use was not associated with clinically significant sequelae and it showed a superior safety profile compared with either dose of pethidine. The study was not powerful enough to detect a difference between 50 mg and 100 mg of pethidine.