Abortion was induced in 60 patients between 8 and 18 weeks gestation using 15(S)-15 methyl PGF2alpha in one of three extra-amniotic administration schedules: 1.0 mg in viscous medium (Tylose), 1 mg in viscous medium (Hyskon) or 0.5 mg in non-viscous medium repeated at 12 hours. Eighty per cent of patients aborted within 24 hours in each group. The overall mean induction-abortion interval (+/- S.E.) was 17.6 +/- 2.0: there was no significant difference between the three groups. Twenty patients treated with 1.0 mg in viscous medium had the catheter removed immediately following the prostaglandin injection and the success rate was not significantly altered. Gastro-intestinal side effects (vomiting in 50%, diarrhoea in 32.5%) were more frequent in the patients treated with the larger dose though the difference was not statistically significant. No significant haematological or biochemical changes were detected during the 24 hours following the start of treatment in 24 patients investigated. Thirty seven of the 60 patients (61.5%) aborted completely and did not require surgical evacuation, and none lost more than 500 ml of blood, nor required transfusion. It is concluded that abortion can be induced with a single extra-amniotic injection of 1 mg of 15(S)-15 methyl PGF2alpha in viscous medium in a large percentage of patients but that the incidence of side effects is high.