Delivers the first uniform diagnostic classification system for conducting FBAs This manual presents a unique pioneering classification system, written by the author of a bestselling textbook on functional behavioral assessment, for school psychologists and other personnel who conduct FBAs for problem behaviors. It renovates the idiosyncratic terminology currently used by school psychologists with a standard classification system for selecting a hypothesis about the function of problem behavior for FBAs. The manual presents a uniform set of functions derived from environment-behavior relations. This includes 13 possible functions within four major categories. For each function, there is a general description, explanation, and illustrative examples of the category. Also included are practice case illustrations to facilitate understanding of how to diagnose the function and its category. Introduces a behavioral classification system for diagnosing the function of problem behaviors Provides consistency for selecting a hypothesis about the function of problem behavior for FBAs Provides general description, explanation, and examples for each category and subcategory An appendix include examples of convergent and divergent validity test procedures for specific functions, with hypothetical data. Sample material that can be copied and used with permission for FBA reports and IEPs are provided for the various diagnostic categories.