BACKGROUND: This study was conducted to evaluate the efficacy and side effects of a new regimen of 800 mu g misoprostol administered intravaginally every 6 h up to a maximum of three doses in 24 h for second trimester pregnancy termination. METHODS: A total of 66 women seeking termination of second trimester pregnancy (30 fetal structural anomaly, six chromosomal abnormality and 30 fetal death) were randomly assigned to one of two treatment groups: (i) intravaginal misoprostol moistened with 3 ml of 5% acetic acid in group A (n = 33); or (ii) intravaginal misoprostol moistened with 3 ml of saline in group B (n = 33). RESULTS: The overall median (range) induction-abortion interval was 10 h (2-46) [10 h (4-35) in 36 live fetuses and 9 h (2-46) in 30 dead fetuses, P = 0.515]. All of the patients in both groups aborted within 48 h (100% success rate). The median (range) induction-abortion interval revealed a significantly faster delivery time (P < 0.001) in group A [8 h (2-24)] than in group B [14 h (3-46)]. CONCLUSIONS: This new regimen of 800 mu g of vaginal misoprostol every 6 h for a maximum of three doses in 24 h was an effective alternative method for second trimester abortion. In addition, misoprostol moistened with acetic acid was significantly more effective than misoprostol moistened with saline.