Twin pregnancy is considered as a risk factor of preterm labor, which is responsible for the high rate of perinatal mortality and morbidity associated with this condition. The objective of this study was to evaluate the role of vaginal progesterone in the prevention of SPB in twin pregnancy. One hundred women pregnant in twins were enrolled for this study. They were divided in 2 groups. Group (1) 50 pregnant women received vaginal progesterone 200mg daily for 10 wks (from the 24th to the 34th week of gestation). Group (2) 50 pregnant women received placebo for the same duration. Transvaginal ultrasound measurement of the cervical length was done at 18-24 weeks gestation.This study showed that the prophylactic vaginal progesterone administration has no significant value in the prevention of SPB in twin pregnancy.