Objective To compare the effectiveness of gemeprost and misoprostol as prostaglandins used in combination with mifepristone for induction of mid-trimester termination.

Design Randomised trial.

Setting Scottish teaching hospital.

Sample One hundred women undergoing abortion between 12 and 20 weeks.

Methods Each woman received 200 mg mifepristone and 36–48 hours later either 1 mg gemeprost vaginal pessary every 6 hours for 18 hours or 4 × 200 μg misoprostol tablets vaginally followed by 2 × 200 μg misoprostol tablets orally every 3 hours for 12 hours. Success was defined as the percentage of women aborted within 24 hours of the first administration of prostaglandin.

Main outcome measures Prostaglandin–abortion interval and side effects.

Results There were no significant differences in median prostaglandin–abortion interval between gemeprost (6.6 hours 95% CI 6.0–10.7) and misoprostol (6.1 hours 95% CI 5.5–7.5) (P= 0.22). The cumulative abortion rates at 24 hours (96%vs 94%, respectively), the surgical evacuation rates (12% and 10%) and the incidence of vomiting, diarrhoea and pain were similar.

Conclusion Two hundred milligrammes of mifepristone followed 36–48 hours later by either vaginal gemeprost or misoprostol is a highly effective way of inducing abortion in the second trimester of pregnancy.