HYPERGLYCINEMIA is a disorder of amino-acid metabolism in which elevated concentrations of glycine are found in the blood, urine, and cerebrospinal fluid. It is now clear that there are at least two forms of hyperglycinemia which probably represent distinct diseases. The first of these to be recognized1 is characterized by recurrent episodes of ketosis leading to coma. More recently, a patient has been described by Gerritsen et al2 who lacked these and other clinical aspects of the syndrome, but had convulsions and diminished excretion of oxalic acid in the urine. Two siblings reported by Mabry and Karam3 may represent the same syndrome, and others have been observed. This hypo-oxaluric form of hyperglycinemia will be considered by Dr. Gerritsen. I shall consider the ketotic type of hyperglycinemia. Manifestations and Characteristics Prominent manifestations of the disease are indicated in Table 1. The most striking feature is that of ketosis,