In the book the conception, advantages and disadvantages of modular training are analyzed, the features, principles and levels of modular training system are described. Modular training system is affected by social, economic and technological developments, which determine the systems' levels. The author describes the levels (national/international, institutional, program and module) and defines the principles of modular vocational training system (utilitarian, cumulative, motivational, training (learning), technological, logical consistency, cooperation, systematic). The modules themselves can not change the teaching and training process; therefore it is necessary to take into account how the training environment is conducive to modular training programs.