Effectiveness of nifedipine in suppressing premature uterine activity was studied on 20 normal pregnant women who received, depending on the frequency of uterine contractions and degree of cervical dilatation, 5-10 mg nifedipine orally 8 hourly till the uterine contractions were abolished followed by 5 mg 12 hourly up to 38 weeks of gestation. Another 20 age, gravida and gestational period matched normal pregnant women received 10 mg isoxsuprine hydrochloride orally 8 hourly till the uterine contractions were abolished, followed by 10 mg 12 hourly up to 38 weeks of gestation. Successful tocolysis was observed in 85% of cases receiving nifedipine in contrast to 40% of women receiving isoxsuprine hydrochloride. The mean time from presentation to delivery and mean birth weight were 21.8 days and 2510 g respectively in isoxsuprine hydrochloride treated cases and 34.2 days and 2750 g respectively in cases treated with nifedipine. In either group there were no serious untoward effects on mother, labour and baby.