Transcranial Doppler (TCD) is a noninvasive diagnostic ultrasound study which uses a 2 megahertz pulsed Doppler transducer to measure the velocity and pulsatility of blood flow within the major intracranial arteries. It has proved to be extremely useful as a screening test or to help confirm the diagnosis of several clinical conditions in infants and children. Some of the proved indications for TCD is for evaluating cerebrovascular occlusive disease especially in screening children with sickle cell disease, hydrocephalus, asphyxia and cerebral edema, confirming brain death, arteriovenous malformations, and vasoplasm. TCD technique, indications, and common pathological findings are emphasized.