Functional behavioral assessment (FBA) is the process of identifying the events in the environment that consistently precede and follow challenging behavior. The use of FBA has increased significantly following the reauthorization of the Individuals with Disabilities Education Act in 1997, which mandated FBAs be conducted when children with disabilities demonstrate challenging behavior. The purposes of this paper are to review the research supporting FBA, describe the components of FBA, and discuss implications for early childhood special education.