This paper is concerned with a well-recognized disorder of infancy and childhood—especially infancy—and commonly called "gastroenteritis of infants." It is characterised chiefly by vomiting and diarrhea; fever is common, and there is a marked tendency to rapid dehydration and to dangerous alterations in the constituents of the blood. It also has epidemic qualities. Its cause is believed to be an enteral infection (various strains of Escherichia coli, Shigella, Salmonella, etc.), though bacteriological examination of the feces may be negative. We have included a number of these "suspected" infections. We have not included in our series examples of vomiting and diarrhea due to feeding problems and parenteral infection. All who have worked for any length of time in children's hospitals will have little doubt that gastroenteritis, in the sense that we are using the term, is, indeed, highly infectious and that it is a potentially dangerous disease. For many years