Individuals with Disabilities Education Act (IDEA) promises all children with disabilities, including those with impeding challenging behavior, a free appropriate public education (FAPE) in the least restrictive environment (LRE). IDEA also promises educational support, in the form of positive behavioral interventions and supports (PBIS) when behaviors impede learning, through an individualized educational program (IEP). The 1997 IDEA amendments and 2004 reauthorization placed explicit requirements on IEP teams to use or consider a functional behavioral assessment (FBA). These requirements state that the FBA process is necessary when a student is removed for more than 10 days from his/her regular educational placement for disciplinary reasons. The purpose of this evaluation brief is to analyze the state law on FBA and to specifically focus on when school teams are required to initiate an FBA. In short, this brief seeks to answer: According to state law, when must an FBA be conducted? Many state law FBA provisions closely mirror those found in the IDEA, appear strictly in the discipline provisions, and leave FBA undefined. Despite best practices outlined in the literature concerning FBA, only a handful of state legislatures and regulators have specifically incorporated the use of FBA into their procedures on evaluation, re-evaluation, or development of behavior interventions and IEPs for a student whose behavior impedes his/her learning or that of others. The following is appended: Selected State Law Definitions of Functional Behavioral Assessment.