Doppler ultrasound when used appropriately is an invaluable tool in monitoring high risk twin pregnancy. There are no recent multicentre randomised controlled trials examining the value of routine umbilical artery doppler (UA), middle cerebral artery doppler (MCA), cerebroplacental ratio (CPR), uterine artery doppler (UtA) and ductus venosus doppler in uncomplicated twins. Thus, there is lack of international consensus in relation to incorporation of doppler ultrasound in the routine surveillance of uncomplicated multiples. In this chapter we will discuss how twins differ from singletons in their growth trajectories and progression of doppler abnormalities. International clinical guidelines are reviewed. Recommendations for doppler surveillance (routine or selective) with reference to recent studies are made.