The efficiency and acceptability of a single-dose, long-acting vaginal suppository containing 3.0 mg of 15-methyl PGF2alpha methyl ester was compared with intra-amniotic administration of 50 mg of PGF2alpha in 100 patients with a second trimester pregnancy termination. Within 24 hours, 78 per cent of the patients in the vaginal group and 92 per cent in the intra-amniotic group had aborted. The mean induction-abortion interval was 17.9 hours in the vaginal group and 15.8 hours in the intra-amniotic group. Gastrointestinal side-effects were more frequent, but the procedure was less painful, with vaginal 15-methyl PGF2alpha methyl ester than with intra-amniotic PGF2alpha. The vaginal route is technically simple for adaptation to large-scale use, but the high frequency of gastrointestinal side-effects still limits the acceptability of 15-methyl PGF2alpha methyl ester in vaginal administration.