Hydrocephalus is distension of the ventricular system of the brain related to inadequate passage of cerebrospinal fluid from its point of production within the ventricular system to its point of absorption into the systemic circulation. Developmental disorders are the most common causes of hydrocephalus, but there are other causes as well. Diagnosis is based on the clinical features and on brain imaging to assess ventricular size and to identify any specific causes. Medical therapy can provide temporary relief but definitive treatment usually involves placement of a ventriculoperitoneal shunt. This article discusses the pathophysiology and management of hydrocephalus.