A case history of the development of a new Kansas state policy on juvenile delinquency illustrates the use of policy impact analysis and suggests four principles to follow in prescriptive policy analysis. A Kansas governor's task force on juvenile delinquency found evidence linking delinquency to undetected health problems (in sight, hearing, speech, or other neurological systems) that are likely to cause school or behavior problems. The task force recommended that child health assessments, using the state's Early Periodic Screening, Diagnosis, and Treatment (EPSDT) program, be made a precondition for entering any Kansas school. To justify its recommendation, the task force used the "social costs" method of policy impact analysis, arguing that EPSDT's costs would be offset by savings in treating and handling juvenile delinquency. From this case history, their own experiences, and the literature, the authors identify four principles of prescriptive policy analysis. The first principle maintains that the primary test of a recommendation is whether it changes existing policy. The other principles state that policy analysts should know their limitations, analyze the impact of doing nothing, and describe both the social or physical process to be changed and the nature of the change. (Author/RW)