It is the object of this thesis to examine Army experience of therapeutic trials. The major factual contribution to this thesis is the section dealing with syphilis therapy in. the Army. For the conduct of this the candidate was wholly responsible, with such clerical assistance as given by junior members of the Army Directorate of Medical (statistical) Research. The same is true of the sections dealing respectively with Malaria and with Internal Derangement of the Knee. The other sections record collaborative investigations in which the candidate participated as a member of a team of investigators.