This was a double-blind randomized control study to evaluate the efficacy of cervical priming by nitric oxide donor before second-trimester induced abortion. One-hundred healthy women with a singleton pregnancy between 14 and 20 weeks of gestation were randomized into either 40 mg isosorbide mononitrate or placebo, given intravaginally 12 h before induction. This was followed by intravaginal misoprostol induction. The induction-abortion interval, abortion rate, side effects and the woman's acceptability of the priming agent were recorded. All women completed the study and there was no severe complication recorded. There was no significant difference in the induction-abortion interval and abortion rate between the two groups. Isosorbide mononitrate group reported significantly more side effects of headache. More than 90% of the women in both groups found the priming agent acceptable. The application of intravaginal nitric oxide donors prior to the prostaglandins induction did not significantly improve the second-trimester induced-abortion process.