Diazepam 0.2 mg/kg, diazepam 0.3 mg/kg or a placebo were administered i.m., during labour, in a double-blind fashion to 28 multiparous patients. Although there were no significant differences in the requirements for i.m. pethidine during labour, diazepam was associated with a superior quality of pain relief. Diazepam 0.3 mg/kg i.m. produced no obvious adverse effects upon the neonate.