Accurate, early screening is a prerequisite for indicated interventions intended to prevent development of externalizing disorders and delinquent behaviors. Using the Fast Track longitudinal sample of 396 children drawn from high-risk environments, the authors varied assumptions about base rates and examined effects of multiple-time-point and multiple-rater screening procedures. The authors also considered the practical import of various levels of screening accuracy in terms of true and false positive rates and their potential costs and benefits. Additional research is needed to determine true costs and benefits of early screening. However, the results indicate that 1st grade single- and multiple-rater screening models effectively predicted externalizing behavior and delinquent outcomes in 4th and 5th grades and that early screening is justified.