For the purpose of this discussion, "criminal thinking" is defined as "thought content and process conducive to the initiation and maintenance of habitual lawbreaking behavior." The paper first reviews three reliable and valid self-report measures of criminal thinking with ties to the three precursor models: differential association, neutralization, and criminal personality. The self-report instruments are the Criminal Sentiments Scale (CSS), the Psychological Inventory of Criminal Thinking Styles (PICTS), and the Measures of Criminal Attitudes and Associates (MCAA). Future research should determine whether these instruments duplicate one another or measure distinctive characteristics or criminal thinking. While acknowledging that no single model of criminal thinking will satisfy all researchers and clinicians, the author outlines a model that he has found most helpful. It is based in the concept of "schemes," a term borrowed from Piaget (1977). A "scheme" is defined as a basic unit of meaning that underlies lifestyle. Schemes develop through a person's interactions with his/her environment. The childhood precursors of the crime scheme can be traced to a child's understanding of rules and rule-breaking and such fundamental schemes as perceptions of right and wrong. With experience and practice, these schemes become more precise, differentiated, and abstract. 1 figure and 59 references