The Physical principles and techniques of magnetic and ultrasonic flaw detection in rails are given. The intended use, working principles and layout of various rail flaw detector systems and the procedure for working with them are described. The methodology of rail inspection, both in the field and at railwelding facilities is also described. The repair of flaw detection equipment on the railroads is examined. The book has been approved by the Chief Administration of Educational Institutions of the MPS (Ministry of Railroads) as a textbook for rail transportation technical schools and by the Academic Council of the State Committee of the USSR Council of Ministers responsible for professional-technological education as a manual for individual- team instruction production workers. It will be helpful to track facility workers involved in the inspection of rails.