The standardization of pH has been achieved in Great Britain 1 , in the United States 2 -5 , and recently also in Japan 6 • In their essential elements, the three standards are in agreement; only differences of detail exist. I t is the object of this report to summarize, for the information of all national groups interested in pH, the extent of standardization already achieved and to indicate how this area of agreement could perhaps be extended to other conceptions related to pH.