Phenylpyruvic oligophrenia is a heritable disorder characterized by mental retardation and the excretion of large amounts of phenylpyruvic acid in the urine. It was first described by Folling in 1934.12 A few years later, Jervis18 reported in detail a series of 50 patients with this disorder. The term "phenylketonuria" is replacing "phenylpyruvic oligophrenia" so as to make the designation of this abnormality consistent with those applied to other hereditary anomalies of metabolism, such as alkaptonuria, cystinuria, galactosuria, etc. Foiling12 and Jervis18 stressed descriptions of skin disorders "consisting of more or less diffuse eczema." Our investigation of phenylketonuria was carried out in an attempt at classifying these skin disorders, and in order to possibly correlate them with the known error in phenylalanine metabolism. This problem is of particular interest to dermatologists, since phenylalanine normally is metabolized to tyrosine, a melanin precursor. The incidence of phenylketonuria is about .005%