BACKGROUND: Prolonged labour is still a common problem in our environment and its sequelae remain an important cause of maternal and foetal morbidity and mortality. Obstetricians are still exploring ways of shortening the duration of labour so that the incidence of prolonged labour is reduced. Hyoscine -N-Butylbromide, an antimuscarinic agent has been used by some obstetricians to shorten the duration of first stage of labour, but controversies still exist regarding its effectiveness. OBJECTIVE: To assess the effectiveness of Hyoscine-N- Butylbromide on the duration of the first stage of labour in nulliparous women. METHODOLOGY: A randomised double-blind controlled study was carried out on 126 nulliparas admitted in active phase of labour. The women were recruited and randomised into study and control groups based on the inclusion and exclusion criteria. The recruited patients were given intravenous Hyoscine-N- Butylbromide 20mg(1ml) or 1ml of sterile water as placebo in active phase of labour. The duration of first stage of labour and rate of cervical dilatation were assessed. The maternal vital signs, foetal heart rate, APGAR scores at first and fifth minutes, and side effects in both study groups were assessed.