Background: induction of labor refers to the process of artificially initiating uterine contractions prior to their spontaneous onset to effects progressive effacement and dilatation of the cervix and ultimately, delivery of the baby. Aim of the Work: to establish whether a single dose of dexamethasone (8mg) intra-muscularly plays a role in shorting the duration interval between initiation of labor induction and beginning of the active phase of labor in primigravida full-term pregnancy. Patients and Methods: this clinical interventional randomized case-controlled trial was conducted at El Hussien University Hospital during the period from July 2017 to March 2018. One hundred twenty full term & post-term (≥ 40 weeks) nulliparous women were included in this study and divided into the following: Group I (Dexamethasone group) injected with 2 ml (8 mg) of the product (dexamethasone) 6 hours before initiation of labor induction and Group II (Control group) was not receive dexamethasone or any other cervical ripening agent. Results: our results showed that the intramuscular administration of dexamethasone appears to shorten labor duration. Conclusion: single intra-muscular injection of two ml. (8mg.) of dexamethasone before induction of labour appears to shorten labor duration