The Compleat Infidel is a study in discursive psychology (Edwards and Potter, 1992: Potter and Wetherell, 1987). Its topic is defensive practice in the discourse of marital and para-marital infidelity. The objectives were threefold: to document and explicate the discursive terrain: to demonstrate an application of the principles of discursive psychology; to develop a critique of selected areas of social science generally and social psychology in particular. A database of more than 230 samples of discourse drawn from heterogeneous sources including newspaper reports, works of popular psychology and original research interviews was amassed and subjected to discourse analysis according to the methods described by Edwards, Potter and Wetherell. The findings are that in contemporary, Anglo-American discourse five discrete types of construction are routinely produced to defend infidels and infidelity: (1) non-events; (2) isolated episodes; (3) special categories of self; (4) specific reasons: (5) generic rationales. The variability within and between these constructions reflects their orientation to differing aspects of the interactional context and their different functions therein. Relevant aspects of context include: interviews and other question-and-answer sessions; silent, anonymous and sympathetic recipients, tabloid and broadsheet news; contexts of argument and debate. The range of defensive functions being performed includes: (1) exoneration, (2) appeal to mitigating circumstances: (3) appeal to diminished capacity or diminishe d responsibility; (4) defence of provocation: (5) justification. The conclusions are that social scientific investigations of infidelity, adultery, cheating, extramarital sex and similar phenomena must acknowledge that discourse is action orientated if a complete and coherent analysis is to be achieved. This conclusion is shown to be relevant to endeavours in sociology, evolutionary psychology, social cognition, the psychology of individual differences, psychopathology and applications of psychology in public health surveys and couples therapy, as well as studies of discourse that are informed by feminist and other varieties of social cons tructionism. The contribution of The Compleat Infidel to the accounts literature and to action orientated approaches to discourse such as discursive psychology is discussed and directions for further research are recommended.