Forty-four patients aged from one month to 16 years suffering from arterial stroke were carefully studied for any hereditary and acquired risk factors for stroke. No physiologic anticoagulant deficiency or antiphospholipid syndrome was found. Two patients had mitochondrial diseases (MELAS). Six patients had migraineous stroke. Migraine and thrombotic disease in the families of the patients were not more prevalent than in the families of the controls. Preceding infections occurred in 34% of the patients, that is, significantly more common than in the age-matched controls. Two children had borreliosis. Repeat strokes occurred particularly in patients with migraine (n = 4) and MELAS (n = 2). The hereditary factors studied here seem to play only a minor role in pediatric patients. Repeated strokes have a varied etiology and are difficult to prevent. Important triggers of strokes are infections.