Conventional tests and testing procedures are used predominately to determine eligibility for early intervention and early childhood special education programs and services. Such traditional tests must have critical attributes to ensure accurate and representative measurements of the capabilities of infants, toddlers, and preschool children who have developmental delays and disabilities. Researchers and critics have questioned the presumption that conventional tests have the requisite practice-based evidence to justify their use for early intervention eligibility. In this updated research synthesis, we reviewed the available research literature on the most frequently used conventional tests and found 44 studies exploring their technical adequacy related to eligibility determination; then, we identified and applied well-known early childhood professional standards for developmentally appropriate assessment to the research literature on these conventional tests/editions to determine their fit with early childhood intervention philosophy, purpose, and practices. The results of our qualitative study and research synthesis raise serious questions about the lack of critical qualities, field validation, and evidence base of conventional tests and testing to fulfill the purpose of early intervention eligibility determination. Implications for professional practices in early childhood intervention, particularly eligibility determination, are discussed with relevant perspectives on policy and research issues. (author abstract)