A large number of individuals took part in the development and application of the methods of accident investigation and prevention outlined in the following paper. Commodore G. d'Erlanger, C.B.E., O.C. Air Transport Auxiliary, took a major part in the general evolution of the procedure; Air Vice-Marshal Sir Lawrence A. Pattinson, C.B., D.S.O., M.C., D.F.C., with his great knowledge of R.A.F. procedure, was responsible for the production of the A.T.A. manual “Instructions for Reporting Flying Accidents, Forced Landings, Aircraft Defects and Casualties”; and starting from scratch, a very competent Secretariat, consisting of Flt/Capt. G. Merton, F/O D. G. Brinjes and F/O J. W. Gibbs, were responsible for the great amount of work involved in working the machine and in the eventual production of the data and information summarised herein. The Chief Medical Officer, A.T.A., Cmdr. A. Buchanan Barbour, is in general responsible for those paragraphs of this paper covering the field of aviation medicine.