In order to further evaluate the usefulness of the antiprogestogen, mifepristone, as a cervical ripening agent, a double-blind multicentre study was undertaken of 230 primigravid women with 10-12 weeks amenorrhoea who were randomly assigned to receive either 0 (placebo) or 200 mg of mifepristone 36 hours before surgical pregnancy termination. Fifteen women who did not fulfil all of the selection criteria were excluded from analysis. In the mifepristone group (N = 105) 12 women experienced some pre-operative vaginal bleeding as compared with only one subject in the placebo group (N = 110), but only one of these 12 women described the bleeding as more than her usual menstrual flow. In mifepristone-treated women the cervix was about 1 mm more dilated at operation and further mechanical dilatation was needed less frequently than in placebo-treated controls. High resistance during further mechanical stretching was encountered significantly more often and at a smaller cervical diameter in the placebo group than in the women given mifepristone. Also, dilatation was reported by the operating surgeons to be easier in women given the antiprogestogen. Other significant differences included a shorter operation time, lower peroperative blood loss and less frequent use of analgesic drugs post-operatively in the mifepristone group. Post-operative complications, the duration of post-operative bleeding and the interval to the first menstruation were similar in both groups. The results confirm that the antiprogestogen, mifepristone, is an effective cervical ripening agent which deserves further study in comparison with the currently used methods, i.e. prostaglandins and osmotic dilators.