OBJECTIVE:To compare intramuscular oxytocin alone and intramuscular oxytocin with ergometrine (Syntometrine) for their effect in reducing the risk of postpartum haemorrhage when both are used as part of the active management of the third stage of labour. DESIGN:Double blind, randomised controlled trial. SETTING:Two metropolitan teaching hospitals in Perth, Western Australia. SUBJECTS:All women who expected a vaginal birth during the period of the trial. Informed consent was obtained. MAIN OUTCOME MEASURES:Postpartum haemorrhage, nausea, vomiting, and increased blood pressure. RESULTS:3497 women were randomly allocated to receive oxytocin-ergometrine (n = 1730) or oxytocin (n = 1753). Rates of postpartum haemorrhage (> or = 500 ml or > or = 1000 ml) were similar in both arms (odds ratio 0.90 (0.82); 95% confidence interval 0.75 to 1.07 (0.59 to 1.14) at 500 ml (1000 ml) threshold). The use of oxytocin-ergometrine was associated with nausea, vomiting, and increased blood pressure. CONCLUSIONS:There are few advantages but several disadvantages for the routine use of oxytoxinergometrine when prophylactic active management of the third stage of labour is practised. Further investigation of dose-response for oxytocin may be warranted.