Background: Many studies proved that the administration of isosorbide mononitrate in combination with misoprostol might increase the success rates of abortion and delivery and help in the reduction of side effects of misoprostol. Objective: To ascertain if misoprostol and intravaginal isosorbide mononitrate (IMN) intravaginally administered together can reduce the time needed to induce labor in postdate women. Patients and Methods: One hundred postdate pregnant women with unfavourable cervixes who were due for labor induction, in Labor Ward, Ain Shams Maternity Hospital, were selected and randomly allocated to receive IMN 40 mg with misoprostol 25 µg or misoprostol 25 µg alone by vaginal administration. The duration of induction to the active phase is the primary result. To match the two groups, Bishop's score, gestational age, parity, and mother's age were taken into consideration. Results: Women who took IMN with misoprostol had substantially shorter induction to active phase lengths (10.6±1.5 against 8.8±1.3 p 0.001) and from the beginning of induction to the time of delivery (17.2±2.3 versus 12.2±2.7 p 0.001) than those who got misoprostol alone. There was no statistically significant difference between the two groups regarding uterine contractile anomalies including tachysystole, hypertonus, and hyperstimulation. The risk of maternal side effects such flushing, hypotension, tachycardia, diarrhea, or postpartum hemorrhage was not significantly different between the two groups, despite the presence of a substantial variation in the rate of headache. 2 patients (4%) had headache in group A (misoprostol alone), compared to 15 (or 30%) in group B (IMN with misoprostol). Conclusion: The use of IMN in combination with misoprostol in the induction of labor is effective in the reduction of the duration of induction and safe on the mother and fetus.