The book provides material for a one-year course (three or four lecture hours a week) in quantum field theory. However, the text is split in a natural way into two parts. Part 1 deals with Lagrangian (canonical) field theory, including Feynman graph techniques and perturbation theory. Part 2 is concerned with more advanced and more modem topics, such as the various "axiomatic" approaches to the theory, general properties of collision amplitudes, and the fundamentals of dynamical calculations in hadron physics. Thus, Part 1 (which is complete in itself) can be used in an introductory course, and Part 2 in an advanced course (or special seminar), each course requiring one semester. (Particular chapters of Part 2 can also provide material for short seminars.) Part 2 refers only occasionally to Part 1 so that anyone familiar with elementary quantum field theory could use it independently of Part 1. Both parts are suitable for self-study.