Despite the considerable social and health costs associated with drinking alcoholic beverages, little is known, in detail, especially in neuroscience terms, about why ethanol reinforces ethanol-intake. Relatedly, little is known concerning why certain individuals consistently drink to the point of toxicity, i.e., lose control of drinking. The basic question of why individuals drinks is central to eventually developing prevention-programs and therapy directed toward remediating alcohol abuse and alcholism. Modern theories of addictions stress the capability of addicting agents, including ethanol, to be positively reinforcing. The plan is to develop a procedure so that ethanol's positively reinforcing characteristics can be reliably indexed and, therefore, set the stage for studying the neural mechanisms of that positive reinforcement. Among the planned studies is to ask which antagonists of neurochemical systems would reduce alcohol's capability to be reinforcing. Preliminary data-collection demonstrate conclusively that small doses of certain opioids increase rats' propensity to drink alcoholic beverages. These findings add to a considerable body of research indicating that alcohol may interact with endogenous opioid systems to achieve some of its effects, particularly those associated with propensity to drink large amounts of alcohol. Research is planned that extends the initial findings that certain opioids increase propensity to drink alcoholic beverages. In particular, there is a plan to extend the finding that large doses of morphine given with diprenorphine, an antagonist for many of morphine's effects, lead to much greater intakes than small or large doses of morphine by themselves, a finding indicating only one type of opioid receptor may be involved in opioid-potential of propensity to drink alcoholic beverages. In the experimental situation used and under the influence of certain drugs, the rats drink to point of showing clear signs of intoxication. The proposed research, therefore, is seen as part of an effort to understand why individuals drink to the point of engendering considerable risk to health and social well-being.