To explore the effectiveness of nifedipine compared with atosiban for tocolysis in preterm labour. A systematic review of randomised controlled trials with meta-analysis using adjusted indirect comparison. Six hundred and seventy-nine women recruited in nine randomised trials evaluating the effectiveness of nifedipine versus beta-agonists, and 852 women recruited in four trials of atosiban versus beta-agonists. There were no trials comparing nifedipine directly with atosiban. We performed meta-analysis with a technique involving an adjusted indirect comparison between nifedipine and atosiban using beta-agonists as the common comparator. This approach preserves the benefit accrued by randomisation in the original comparisons. Reduction in neonatal respiratory distress syndrome and delay in delivery by 48 hours. Nifedipine tocolysis was associated with a significant reduction in respiratory distress syndrome compared with atosiban (OR 0.55, 95% CI 0.32-0.97). It also increased the number of women whose delivery was delayed by 48 hours (OR 1.20, 95% CI 0.73-1.95), although this result was not statistically significant. When indirectly compared with atosiban, nifedipine tocolysis is more effective. In the absence of a direct comparison, our analysis provides a way to explore the potential benefits of nifedipine versus atosiban.