Vaginal and intramuscular administration of prostaglandin analogues are routinely used for dilatation of the cervical canal prior to vacuum aspiration in first trimester abortion. Whether the same procedure is also useful during the first weeks of the second trimester has been much less investigated. In the present study, 127 women in the 13th and 14th week of pregnancy were pretreated with 3 mg 9-deoxo-16,16-dimethyl-9-methylene PGE2 administered vaginally 12 hours before surgery. At surgery the cervical canal was dilated to 9.8 mm +/- 2.5 mm (mean +/- SD) and the evacuation of the uterus was uneventful. In 21% of the patients vaginal bleeding occurred prior to the operation. The mean blood loss at surgery was 49 ml and exceeded 100 ml in only 6 patients. Gastrointestinal side effects were rare but analgesic injections were demanded by 29% of the patients during the pretreatment period. No subsequent curettage was performed during the follow-up period but 2 patients (1.6%) were readmitted because of post-abortion endometritis. It can be concluded that after pretreatment with PG, vacuum aspiration can be safely performed during the first weeks of the second trimester.