Under federal special education law, before a school district may discipline a student with a disability for greater than 10 days, it must first determine whether the student's actions were a manifestation of his or her disability (IDEA, 2004). This requirement, referred to as manifestation determination review (MDR), aims to ensure that students with disabilities do not experience a significant disciplinary change in placement for actions that are caused by their disabilities. This article will discuss the evolution of the legal standard and the policy implications of a study that examined 80 MDR decisions in one large urban school district.