This little volume contains the proceedings of a meeting of the Society for the Study of Inborn Errors of Metabolism, a group of British physicians and chemists, held in Liverpool on Sept 16, 1964. It is a companion piece to the report of the first meeting in Sheffield, in 1963, Neurometabolic Disorders in Childhood. The first chapter, by Dr. Nina A. J. Carson of Belfast, reports a chemical survey of 2,920 severe mental retardates in northern Ireland. Urine specimens were screened for reducing substances, phenylpyruvic acid, ketones and keto acids, protein, sulphur-containing amino acids (it is not clear that all other amino acids were studied), porphobilinogen, calcium, indican, and acid mucopolysaccharides. Sixty-nine cases of phenyketonuria were identified for a surprisingly high incidence of 2.4%. There were ten cases of homocystinuria, three cases of hyperglycinemia, two cases of arginosuccinicaciduria, one case of Lowe's syndrome, and 38 generalized amino-acid-urias which are not