The purpose of this work is to present in some detail methods of dealing with cases requiring change of intestinal flora that have been successfully employed by the writer and his colleagues in the treatment of some thousands of patients at the Battle Creek Sanitarium. All the methods and measures recommended have been thoroughly tried and proven to be efficient in meeting the indications for which they are recommended. The regimens which have been worked out as the result of many hundreds of experiments extending over forty years of active practice, if used with the proper precautions, will rarely fail to produce the results expected of them, and generally the results will more than meet expectations. Contents: bacteria; how the body defends itself; changing and reforming the intestinal flora; milk regimen; technique of the milk regimen; application of the milk regimen in the treatment of various disorders; fruit regimen and disorders in which it is indicated; fasting; antitoxic diet; relief of constipation; exercise; eating for health; rice regimen; potato regimen.