In a report by representatives of the Wisconsin State Board of Health on an investigation of an outbreak of gastroenteritis which occurred at Milwaukii in February, 1938, it was concluded, after reviewing extensive epidemiological evidence, that the outbreak was most problably water-borne and it was further recommended that a new standard of quality be adopted for chlorinated water supplies. This study proposes and recommends a new standard with special reference to its possible application to Milwaukee water, and reviews the laboratory results of examinations of this water.