The first step is improving the possibility of replication and assessment of the long-term effects of drug prevention programs is specifying the intervention theory. The theory must identify the basis for the intervention and the target population; suggest short- and long-term outcomes; and describe the linkages among these three variables. Many methods of collecting data on the degree of implementation have been employed. Ideally, several measurement methods assessing multiple indicators should be included to provide a comprehensive evaluation. When reporting on implementation data, researchers should systematically assess personality characteristics, situational variables, and the political context of the intervention. Selection of the appropriate implementation indicators used to judge the degree of operationalization of the theoretical construct should be based on the theoretical foundation of an intervention. The authors illustrate six structural equation models which incorporate data on intervention implementation into the analysis of the relationship between the intervention and outcomes. 6 figures and 22 references