In this chapter, we examine the topics of risk-taking, thrill-seeking, and criminal behaviors through the lens of opponent process theory. Empirical studies have bolstered and challenged the proposed connections between opponent process theory and risky or thrill-seeking actions in the vein of activities such as self-inflicted injury, substance abuse, and even parachute jumping. However, the link between criminal behavior and opponent process theory has been explored on a more limited and speculative basis derived from studies focused more generally on the concept of sensation-seeking behavior. Nevertheless, a review of the extant literature may provide a groundwork for further research into the potential implications of opponent process theory in the context of criminal behavior.