Background: The most favorable method for cervical ripening is not fully agreed upon by practitioners; however, isosorbide mononitrate administration is considered a low-risk method of labor induction for pregnant women at full term. Objective: To evaluate the safety and effectiveness of adding isosorbide mononitrate to misoprostol for cervical ripening in prelabor induction of full term pregnant women in comparison with misoprostol alone. Design: Randomized study. Setting: Ain Shams Maternity teaching hospital. Patients and methods: 120 women were divided randomly into two equal arms of 60 women in each one. Intervention: Patients admitted through the reception room or out patient clinic and they scheduled for induction of labor. Group I were given intravaginal isosorbide mononitrate with misoprostol while group II were given placebo with misoprostol intravaginally.