Non-ketotic hyperglycinemia is one of inborn metabolic errors that manifest by epileptic seizures of difficult control from the first days of life in hypotonic newborn children. The lack of enzyme that catalyzes the conversion of glycine to hydroxymethyltetrahydrofolic acid, carbon dioxid and ammonia, in liver and brain, results in increased concentration of glycine in blood. It is reported in this study a case of non-ketotic hyperglycinemia diagnosticated in neonatal period and characterized by hypotonia and non-controlled multiple seizures. The clinical and eletroencephalographic findings, treatment as well as anatomopathologic study are discussed.