The aim of this study was to investigate the sensitivity of cranial ultrasonography for detecting acute arterial ischemic stroke in term neonates. Thirty-six neonates with gestational age > or = 36 weeks who had cranial ultrasonography followed by computed tomography (CT) or magnetic resonance imaging (MRI) confirming arterial ischemic stroke were identified from a consecutive cohort study of all children diagnosed with arterial ischemic stroke by CT or MRI and seen at Chedoke McMaster Hospital between January 1992 and December 1998 or at The Hospital for Sick Children between January 1992 and December 2000. Cranial ultrasonography demonstrated focal abnormalities in 11 patients, giving the initial cranial ultrasonography a sensitivity of 30.56% for identifying neonates with infarction (95% CI 15.5-45.5%). The sensitivity of cranial ultrasonography performed in the two pediatric referral centers (Chedoke McMaster Hospital and Hospital for Sick Children; n = 19) was higher than that in community hospitals (n = 17) (47.3% versus 11.7%; P =.031). Neonates with suspected infarction should be evaluated with CT or MRI.