Although clinical judgment is often used in assessment and treatment planning, rarely has research examined its reliability, validity, or impact in practice settings. This study tailored the frequency of home visits in a prevention program for aggressive-disruptive children (n = 410; 56% minority) on the basis of 2 kinds of clinical judgment: ratings of parental functioning using a standardized multi-item scale and global assessments of family need for services. Stronger reliability and better concurrent and predictive validity emerged for the 1st kind of clinical judgment than for the 2nd. Exploratory analyses suggested that using ratings of parental functioning to tailor treatment recommendations improved the impact of the intervention by the end of 3rd grade but using more global assessments of family need did not.