Response disequilibrium theory (RDT) is more than just an approach to reinforcement; it is a theory of behavior regulation. RDT assumes that organisms exhibit a measurable behavioral equilibrium that they attain, preserve, or abandon in the face of environmental challenges. RDT offers quantitative models of behavior regulation that predict the effects of these environmental challenges. The basic and predictive disequilibrium models quantify the directionality and extent of behavior change, so researchers and practitioners can a priori identify the constraints that will cause behavior to increase, decrease, or stay the same. Unlike any law of effect predating it, RDT can precisely specify the causal conditions for reinforcement and punishment effects. Moreover, its adaptive and conservation models quantify these outcomes and pave the way for generating falsifiable hypotheses about behavior regulation. The following chapter does three things: (1) it defines behavior regulation as an alternative to previous accounts of reinforcement, (2) it explicates the use of disequilibrium models to arrange contingencies and predict their outcomes, and (3) it introduces the conservation model to quantify the effects of constraints beyond the standard two-response contingency situation. The conservation model is applicable to multiple-response situations, where the organism regulates by substituting one behavior for another. In a re-analysis of basic and applied data to test these models, we provide readers with a Microsoft Excel spreadsheet ( https://osf.io/ujnwq/ ) to follow along and make their own predictions.