Eight project evaluations comprising of the California school-based risk-reduction programs met the following methodological requirements for evaluation research: comparison groups; pretesting; participant tracking; control of attrition; dependent variable validity; and effect size computation. Of these eight studies, six were based upon a rational model and two upon a developmental model of intervention. The major results of this study show that the rational model programs impact more on knowledge and less on attitudes and behavior, whereas developmental programs impact more on attitudes and behavior and less on knowledge. At present, the results indicate that the developmental approach, because of its effects on behavior, has more potential for deterring drug use. Further implementation and evaluation is required to clarify the differential effectiveness of different theoretical models on substance abuse interventions. 7 tables and 20 references (Author abstract modified)