Quantum Chromodynamics becomes now – moving into the second decade of the twentyfirst century – a very extended theory with many branches. Therefore, it is impossible to expose in one book the whole QCD with all its branches and applications. On the other hand, it is a rapidly developing theory and for the authors of a book on QCD it is a serious danger to go too close to the border between that which is known with certainty and the domain of unknown. For these reasons, we decided to present in this book some aspects of QCD that are not very closely related to one another. In the selection of these aspects, surely, the individual preferences of authors also played a role.

What is not discussed in this book includes the theory of heavy quark systems – charm, bottom, top mesons and baryons; QCD at finite temperature and density; the problem of phase transitions in QCD; and lattice calculations. The QCD corrections to weak interactions, particularly to the production of W, Z, and Higgs bosons, are also beyond the scope of the book. We intentionally avoided various model approaches related to QCD, restricting ourself to exposition of the results following from the first principles of the theory. The phenomenology of hard processes and of the parton model was only lightly touched on in this book. We refer the reader to our previous book: B. L. Ioffe, V. A. Khoze and L. N. Lipatov, Hard Process, North Holland, 1984, where these topics were considered in detail.