Some infants with perinatal arterial ischemic stroke (PAS) experience development of cerebral palsy (CP), epilepsy, and cognitive impairment, whereas others have a normal outcome. Previous prognostic studies rarely have included all diagnosed cases of PAS within a population. Among 199,176 infants born within Kaiser Permanente from 1997 to 2002, we electronically identified head imaging reports and physician diagnoses suggesting stroke. The diagnosis of PAS was confirmed by review of brain imaging and medical records. Presentation of PAS was considered delayed if symptoms were only noted after 28 days. Outcomes were determined by chart review. Of 40 infants with PAS, 36 were observed over 12 months. Abnormal outcomes included CP (58%), epilepsy (39%), language delay (25%), and behavioral abnormalities (22%). A delayed presentation was associated with increased risk for CP (relative risk [RR], 2.2; 95% confidence interval [CI], 1.2-4.2). Radiological predictors of CP included large stroke size (RR, 2.0; 95% CI, 1.2-3.2) and injury to Broca’s area (RR, 2.5; 95% CI, 1.3-5.0), internal capsule (RR, 2.2; 95% CI, 1.1-4.4), Wernicke’s area (RR, 2.0; 95% CI, 1.1-3.8), or basal ganglia (RR, 1.9; 95% CI, 1.1-3.3). Among infants with PAS, specific radiological findings and a lack of symptoms in the newborn period are associated with increased risk for CP.