Skinner described behavior analysis as the field of values and purpose. However, he defined these concepts in terms of a history of reinforcement and failed to specify whether and how human and nonhuman values might differ. Human values have been seen as theoretically central within a number of nonbehavioral traditions in psychology, including humanism and positive psychology. However, these approaches have failed to provide explanations of the behavior-environment relations involved in valuing that might allow prediction and influence with respect to this phenomenon. Modern clinical behavior analysis in the form of acceptance and commitment therapy (ACT), however, succeeds in providing a functional definition of human values that meets this latter criterion. ACT is rooted in behavior analysis and relational frame theory (RFT) and defines values in terms of verbally established motivation. ACT empirical research into values has begun to blossom in recent years, and ACT-RFT researchers are currently investigating the concept at the most basic empirical level as well as in the applied clinical arena, heralding new interest in and insight into values within clinical behavioral psychology.