The risk of stroke in children screened with transcranial Doppler ultrasound in the United Kingdom is not known. We evaluated a clinician-led program using a risk assessment modified from the STOP protocol. High-risk classification included abnormal velocities in the anterior cerebral artery, and single abnormal scan if initial velocity >220 cm/s (high abnormal) or if preceded by at least 2 conditional scans. In total, 1653 scans were performed in 542 children, followed for 2235 patient-years. Fifty-eight (10.7%) high-risk subjects were identified, including 18 (31%) with high abnormal, and 15 (26%) with previous conditional scans. In 2 (3%), abnormal velocity was restricted to the anterior cerebral artery. The estimated proportion of children at high risk, scanned before 6 years of age was >20%. There were 4 cases of acute ischemic stroke (AIS) and 2 of acute hemorrhagic stroke. The incidence of all stroke, AIS, and acute hemorrhagic stroke were 0.27, 0.18, and 0.09 per 100 patient-years, respectively. The proportion of children at high risk is higher than most previous estimates, partly as a result of our modified risk assessment. About 2 children per 1000 screened with transcranial Doppler ultrasound progress to AIS.