Nonketotic hyperglycinemia is an autosomal recessive disorder of glycine metabolism. Patients generally present in the neonatal period with lethargy, feeding difficulty, hypotonia, apnea, poorly controlled convulsions, and coma. Myoclonic seizures and burst suppression pattern on electroencephalography are major findings of disease, but development of hydrocephalus is not an expected finding. The present case is that of an infant with acquired hydrocephalus, psychomotor retardation, and myoclonic seizures in whom the final diagnosis was nonketotic hyperglycinemia. (C) 2009 by Elsevier Inc. All rights reserved.