Neonatal stroke is defined as a group of heterogeneous conditions in which there is focal disruption of cerebral blood flow secondary to arterial or cerebral venous thrombosis or embolization, between 20 weeks of fetal life through 28th postnatal day, and confirmed by neuroimaging or neuropathological studies [1]. Two types of ischemic neonatal strokes are arterial ischemic stroke (NAIS) and cerebral sinovenous thrombosis (CSVT). The third stroke type is primary bleeding (hemorrhagic stroke). Additional forms of ischemic stroke unique to the perinatal period include periventricular venous infarction (PVI) and presumed perinatal stroke detected in infancy or childhood (both are not discussed in this chapter). Vessels are occluded by thrombosis, embolism, direct trauma, compression, spasm or obliteration by an inflammatory process. Open vessel ischemia, e.g., during hypovolaemia, arrhythmia or asphyxia, is not included in the definition of stroke.