Early drug intervention programs that provided young people with information about drugs and their effects in order to discourage drug use were not successful and, in some cases, were counterproductive, influencing youth to experiment rather than abstain. Research in the mid-1980's revealed that a more effective prevention strategy might be based on the risk factors that make youth more likely to use drugs. This paper describes some of those risk factors. Contextual or Environmental Factors include: Economic/Social Deprivation; Low Neighborhood Attachment and Community Disorganization; Transitions and Mobility; Community Laws and Norms Favorable to Drug Use; and Availability of Drugs. Individual Risk Factors include: Family History of Alcoholism; Poor and Inconsistent Family Management Practices; Anti-Social Behavior and Hyperactivity; Parental Drug Use and Positive Attitudes Toward Drugs; Academic Failure; Low Degree of Commitment to School; Alienation or Rebelliousness; Association With Peers Who Use Drugs; and Favorable Attitudes Toward Drugs. The paper also describes the multiplicative effect of risk factors. For example, the risk of problem behavior when two risk factors are present is approximately four times the risk when there are no factors. When four factors are present, the risk of drug abuse is 10 times greater.