1 The success of early diagnosis and therefore of treatment of phe­ nylketonuria, inevitably suggests the possibility of early screening and treatment of other genetic metabolic abnormalities. This volume contains a summary of papers delivered at a Workshop on "Recent Advances in Screening and Management of Potentially Trea­ table Genetic Metabolic Disorders" held under the auspices of the Com­ mission of the European Communi ties, in London, U. K., on the 17th and 18th March 1983 to consider such possibilities. The Workshop was not aimed at those disorders for which the prin­ ciples of treatment and management have been soundly established, or for which screening procedures are in general use. The papers therefore do not form a comprehensive account of metabolic disorders. The topics for discussion were selected mainly to highlight recent discoveries which might be exploited by concerted approaches between different cen­ tres, especially when the immediate benefits were restricted to only a few centres. Recent reports suggest that about 2% of infants with persistent hyperphenylaninaemia do not respond to treatment by phenylalanine - low diets, and develop severe brain damage. Infants with such "Malignant Hyperphenylalaninaemia" due to one of several genetic causes of tetrahy­ drobiopterin deficiency should be rapidly identi fied since there is evidence that appropriate treatment will prevent brain damage. The Workshop considered how appropriate screening could be made generally available.