The entire work Parsing Theory appears in two volumes, "Volume I: Languages and Parsing" and "Volume II: LR(k) and LL(k) Parsing". The two volumes form an integral work. Volume I is an introduction to the basic concepts of languages and parsing, and it also contains the relevant mathematical and computer scientific background needed in the development of the theory of deterministic parsing; it deals with topics such as algorithms on relations and graphs, regular languages and lexical analysis, context-free languages, left parsers and right parsers, strong LL(k) parsers and their implementation, simple precedence parsers. Volume II contains a thorough treatment of the theory of LR(k) and LL(k) parsing. "Parsing Theory" is a contemporary reference work on the theory of deterministic parsing of context-free languages. It emphasizes the LR(k) and LL(k) methods, which are developed in a uniform manner and pays special attention to their efficient implementation. Construction algorithms for parsers are derived from general graph-theoretic methods. Complexity questions about parsable grammars are analyzed. The work can be used as a textbook for graduate-level and senior undergraduate-level courses on parsing theory and compiler design. A one-semester course on the basic theory of languages and parsing can be taught from Volume I.