This chapter discusses the epidemiology, clinical features and the occurrence of epilepsy in hydrocephalus and porencephaly. The most common causes of antenatal hydrocephalus include malformations of the cerebrospinal fluid (CSF) pathways or, more extensively, the brain, and abnormal events during pregnancy. Acute infantile hydrocephalus can manifest with lethargy, stupor, vomiting, and oculomotor nerve palsy. The relationship between epilepsy and hydrocephalus is complex. In most children hydrocephalus is part of a clinical picture usually characterized by several neurological disabilities, e.g., cerebral palsy, motor problems, and mental retardation; epilepsy can be one of the symptoms of this encephalopathy of varying etiology. Most porencephalic lesions involve both the gray and white matter. Multicystic encephalomalacia or multicystic encephalopathy is another term used to define multiple cavities that involve large parts of the cerebral hemispheres. Epilepsy also occurs in approximately 10-30 percentage of infants with porencephalic lesions.