The German edition of our book entitled Operative Frakturen behandlung by M. E. MUELLER, M. ALLGOEWER and H. WILLENEGGER (Springer, Berlin . Goettingen . Heidelberg, 1963) has been out of print now for more than three years. We are planning a new edition which will deal with the collective experience of 14,000 new cases, all treated by internal fixation, and will include the newest developments in the field of internal fixa tion. However, it will be some time before this new edition can be published. Increasing demands for a description of the AO technique of internal fixation has stimulated us to publish this manual. In it we shall describe in a comprehensive but somewhat apodictic mann er the principles and techniques of the AO methods of fracture treatment and reconstructive surgery, which in our hands, have stood the test of time. The book is written in a somewhat abbreviated style. It cor responds in subject matter to the teaching given at the AO courses in Davos, but deals with each subject more thoroughly. We have dispensed with pictures of the instruments, as these may be found in the Synthes Catalogue *. This manual should be regarded as the product of collective experiencc, containing new thoughts and new discoveries from basic research. In considering the risks of mistakes and dangers, we can only reiterate what we have already stated in Technique of Internal Fixation of Fractures : Open treatment of fractures is a valuable but difficult method which involves much responsibility.