This is a revision of a competing renewal application which was approved[unreadable] but not funded. In this revision we have made every effort to respond[unreadable] to the critiques of the prior review.[unreadable] Behavioral economics, the application of microeconomic principles to the[unreadable] study of behavior, has value for the field of drug dependence. The value[unreadable] stems from (1) its ability to integrate the effects of independent[unreadable] variables into a singular term, referred to as unit price, and (2) its[unreadable] ability to specify conditions under which choice of a drug vs. a non-drug[unreadable] reinforcer varies from being probable to improbable. The former suggests[unreadable] the parsimony of this approach; the latter suggests its utility in[unreadable] accounting for the selection of drug vs. other reinforcers.[unreadable] The purpose of this proposal is two-fold. The first purpose is to[unreadable] continue our basic research on unit price. We will examine whether[unreadable] several important operations that have yet to be incorporated into unit[unreadable] price (e.g., punishment, reinforcer delay, & probability of[unreadable] reinforcement) can be parsimoniously integrated. These experiments will[unreadable] demonstrate the generality and define the limitations of unit-price.[unreadable] The second purpose is to examine the utility of behavioral economics in[unreadable] the evaluation of medications for the treatment of drug dependence. We[unreadable] will examine the effect of agonist and antagonist treatment on the[unreadable] economic measure of elasticity (the responsiveness of drug consumption[unreadable] to unit price). This new measure, elasticity, may provide an index of[unreadable] whether a medication renders drug use more sensitive to cost factors in[unreadable] the environment. Further, we will examine whether the behavioral-[unreadable] economic determinants of drug choice can assist in assessing the[unreadable] effectiveness of medications under different environmental conditions and[unreadable] whether those determinants can be used to develop a laboratory analog of[unreadable] conditions that promote patient entry into treatment. These experiments[unreadable] will put what we have learned about behavioral economics into the service[unreadable] of assessing medications for the treatment of drug dependence. Moreover,[unreadable] the behavioral-economic determinants of drug choice will allow us to[unreadable] assess and characterize medications under conditions that may more[unreadable] closely approximate clinical conditions than do current assessment[unreadable] models. Finally, developing an assay to assess factors that determine[unreadable] entry into treatment may be useful for any form of treatment.[unreadable] Overall, the continued assessment of the basic factors related to the[unreadable] behavioral economics of drug self-administration and the application of[unreadable] those factors to address medication development provide an important[unreadable] opportunity to explore and utilize this new approach.[unreadable]