Universal screening is designed to be an efficient method for identifying preschool students with mental health problems, but prior to use, screening systems must be evaluated to determine their appropriateness within a specific setting. In this article, an evidence-based validity framework is applied to four screening systems for identifying preschool students with mental health problems. The framework is influenced by the most recent standards for educational and psychological testing, research on test accessibility, and considerations for evaluating screening systems. Suggestions are provided for evaluating the accessibility (Step 1), reliability (Step 2), construct validity (Step 3), and consequential validity (Step 4) of an instrument. Other factors for consideration (i.e., developmental stage, incremental validity, and generalizability) are also identified. Special attention is given to conditional probability indices, which are highly relevant to evaluation of screening systems, given the dichotomous nature of decision making in preschool mental health. The authors suggest that this framework be used, along with specification of the construct of interest and characteristics of the environment, to identify the appropriate method to be used for each preschool screening decision. © 2011 Wiley Periodicals, Inc.