Author Dennis Organ pioneered theories regarding the character and causes of the spontaneous, largely discretionary, often mundane contributions that participants make to organizational effectiveness in journal articles and his previous 1988 text, building on earlier work by Chester Barnard, Daniel Katz, and Robert Kahn. By the early 1990s, it became apparent that the concept of Organizational Citizenship Behavior was evoking considerable interest among researchers in organizational psychology. No doubt some of this interest can be attributed to the long-held intuitive sense that 'job satisfaction matters'. From 1983 to the present time, over 355 articles have been published on Organizational Citizenship Behavior or its conceptual cousins. Interestingly, over half (187) of these papers have been published since 2000. Thus, there is every indication that the interest in Organizational Citizenship Behavior (OCB) has continued unabated, if not intensified. OCB has become a foundation for concepts in Organizational Studies. This text builds on work that has been done on the subject in recent years and seeks to update the record about OCB. The book will provide a 'one-stop shopping' resource for teachers, scholars, and graduate students interested in OCB, whether because of application or research purposes. But the book will also offer an important perspective to the reflective practitioner who seeks an understanding of broad conceptual insight on this key topic.