Impaired glucose tolerance was shown to be present in a proportion of children with cystic fibrosis more than 30 years ago (Andersen, 1938), though symptomatic diabetes mellitus was not recognized as a complication until 1955(Schwachman and Leubner, 1955). This paper presents the results of blood glucose and serum insulin levels after oral and intravenous glucose, and after intravenous glucagon...