The authors compare the efficiency of two drugs in the treatment of threatened premature labour, the one being the calcium inhibitor (nifedipine) and the other a beta-mimetic drug (ritodrine). 62 patients after random selection were divided into two groups: 32 treated with ritodrine and 30 treated with nifedipine. The treatment was carried out over 7 days. The success rate was similar in both groups -72% for the ritodrine group and 63.33% for the nifedipine group. Women receiving nifedipine had slightly greater gain in weeks, six as against five for ritodrine. The side effects which were often found with nifedipine were; hot flushes (in 10 cases) and headaches (4 cases). These symptoms appeared 15-30 minutes after the first dose and were transitory. No neonatal complications were found. The ease with which a calcium inhibitor can be given suggests that it should be used more frequently in the treatment of threatened premature labour and particularly when there are contra-indications to the use of beta-mimetic drugs.