This chapter moves toward defining high-risk youth as young persons with low probabilities of gaining an education, getting a job, parenting effectively, or being able to participate in the political process. Five snapshots are presented of the latest information on the prevalence of the five categorical behaviors of interest: (1) substance abuse, including smoking, drinking, and drugs; (2) sexual behavior; (3) delinquency/violence; (4) depression/suicidal ideation; and (5) school failure. The chapter summarizes recent attempts to examine the interrelationships between and co-occurrences among these behaviors. Risk factors or predictors are examined to determine the attributes of high-risk youth across behavioral domains. Protective factors which foster resiliency to the consequences of high-risk behaviors are described, including: (1) attachment to a caring adult; (2) independence and competency; (3) high aspirations; and (4) effective schools. The chapter offers observations about the shaping of prevention programs in the context of Healthy People 2000. The chapter notes that the trends in prevalence of risky behaviors during the past decade are not encouraging, and suggests the need for much more intensive and large-scale replication of effective prevention programs, using proved components that cut across categorical domains. Contains 30 references. (SD)