The study used three data sets containing up to five ethnic groups to determine the degree to which risk and protective factors are equally reliable and valid predictors of drug use and delinquency across gender and ethnic groups. It evaluated congeneric measurement models and structural equation models to determine whether the factor structures for these measures and their covariances with measures of drug use and delinquency were equivalent across gender and ethnic groups. Half of the risk and protective factors included in the analysis were equally reliable across gender and ethnic groups. In terms of the magnitude of the associations, no substantive differences were found in the validity of risk and protective factors for drug use and delinquency. Differences in the validity of risk and protective factors were more prevalent for delinquency than for drug use. However, all differences were substantively trivial. The study concludes that measures of preventive program effectiveness are invariant across gender and ethnic groups. Notes, tables, figures, references