Cerebrovascular disorders are increasingly recognized as important causes of mortality and morbidity in the pediatric population. Risk factors for stroke in childhood are different from those in adults. Human chorionic gonadotropin is a polypeptide hormone produced by the human placenta and is composed of an alpha-subunit and a beta-subunit. Pregnyl (human chorionic gonadotropin for injection) is a highly purified pyrogen-free preparation obtained from the urine of pregnant females. Ischemic cerebral infarction is seen in the young infertile male and female patients after gonadotropin treatment. The authors describe the case of a boy with right-sided hemiparesis following Pregnyl injection and discuss its possible pathogenetic mechanisms.