Procedures for using a decision algorithm for determining whether an infant or toddler is eligible for Part C early intervention is the focus of this eligibility determination practice guideline. An algorithm is a step-by-step problem-solving procedure or decision-making process that results in a solution or accurate decision in a finite number of steps. A decision algorithm involves a set of decision-making questions where each decision (answer) yields a yes or no result. The particular procedures used to develop the decision algorithm are based on findings from a practice-based research synthesis examining the accuracy of different decision-making processes. The process and procedures described in the guide are designed to shift focus away from gathering information not needed to make an eligibility determination toward a more informed, logical approach to enrolling eligible children in early intervention. Diagram and questions are appended. (Contains 2 figures.) [The Tracking, Referral and Assessment Center for Excellence (TRACE) is funded by the U.S. Department of Education, Office of Special Education Programs.]