The mission of the Center for Education and Drug Abuse Research (CEDAR) is to delineate the etiology of Substance Use Disorder (SUD). Biobehavioral processes and environmental factors are comprehensively assessed prior to first exposure to alcohol and drugs, and subsequently during the period of substance use behavior leading ultimately to a diagnosis of SUD. Employing a prospective paradigm enables clarifying the factors influencing the transition from no use to substance use to SUD. From the practical perspective, upon completion of this longitudinal investigation, the individual risk for succumbing to SUD can be quantitatively specified across different stages of development. Youth who are at high risk for SUD can thus be accurately and objectively identified for prevention intervention. This monograph describes several facets of CEDARs ongoing research program. To illustrate the breadth of ongoing investigation, the articles address the genetic, biochemical, psychological, and environmental factors influencing the risk for SUD. In addition, new instrumentation developed at CEDAR for identifying youth at high risk for SUD is described. (GCP)