Doppler ultrasound has many types and many applications in obstetrics. Fetal venous and cardiac Doppler are now used side to side with arterial Doppler. The most common studied vessels are : Umbilical artery, uterine artery, middlecerebral artery, aorta, inferior vena cava, ductus venosus, umbilical vein with flowvelocity waveforms at the level of atrio-ventricular valves. Doppler velocimetry is now considered the corner stone in :1- Diagnosis and management of intra-uterine growth restriction (IUGR).2- Screening of placental insuffeciency by uterine artery Doppler.3- Studying the hemodynamic changes associated with discordant fetal growthdue to placental insufficiency and twin-to-twin transfusion syndrome.4- Prediction of pulmonary hypoplasia with preterm prelabour rupture of membranes.5- Prediction of fetal anemia in red cell isoimmunized pregnancies.6- Prediction of pre-eclampsia, (IUGR) and adverse perinatal outcome in maternaldiabetes mellitus with prediction of the presence of hypertrophic cardiomyopathy inthe fetuses of Diabetic mothers.7- Suspecting adverse perinatal outcome in post-term pregnancy.8.Predicting the development of pre-eclampsia, intra-uterine growth restriction(IUGR) and perinatal death in maternal auto-immune diseases.9.Diagnosis of gestational trophoplastic disease , detecting invasiveness, recurrenceand following the effectiveness of chemotherapy.10.Diagnosis of ectopic pregnancy by a new sign in transvaginal Doppler,the leashsign.11. Diagnosis of a lot of fetal congenital anomalies.