Objective(s) : Ascertaining the effectiveness of PCB in acceleration of active phase of labour by determining the duration of active phase of labour and the degree of pain relief. Method(s) : Effect of PCB on pain relief during I stage was studied prospectively in 200 full term uncomplicated pregnant females over a period of 6 months. Its effect on the duration of active phase, 11 and III stage of labour, cervical dilatation, injection - delivery interval, uterine contractions and on mother and foetus was evaluated. The findings were compared with a control group of 200 full term uncomplicated pregnant females in active I stage of labour.