For the past five years we have used a double-balloon device for extraovular instillation of prostaglandin solution for termination of midtrimester pregnancy. In 340 consecutive cases a success rate of 91% (abortions within 24 hours) was achieved, with a mean instillation-to-abortion interval of 17.5 +/- 6.5 (SD) hours in nulliparas versus 12.8 +/- 6.1 in multiparas (P < .005). The instillation of continuous, low-dose prostaglandin solution into the extraovular space resulted in very few side effects and no complications. Furthermore, the technique was used successfully in women who had undergone one or more cesarean sections in the past. The use of prostaglandin E2 (PGE2) resulted in shorter instillation-to-abortion intervals than did prostaglandin F2 alpha (P < .01); 500 micrograms/h of PGE2 solution was needed in nulliparas, whereas 250 sufficed in multiparas.