Since submission of the article, "Hypoelectrolytemia and metabolic alkalosis in infants with cystic fibrosis," and, during the first eight months of academic practice, I have diagnosed six cystic fibrosis infants under 1 year of age, four of whom had documented episodes of hypoelectrolytemia and severe metabolic alkalosis. The data are included in the Table. Cases 1 and 2 had recurrent episodes of metabolic alkalosis before the diagnosis of cystic fibrosis was made. Cases 2 and 4 are black infants, in whom the diagnosis of cystic fibrosis would not have been suspected, had not the association between cystic fibrosis and metabolic alkalosis of infancy been recognized.