This guide shows how principles of functional assessment can be applied to behavior problems of students with mental retardation to identify the behavior's purposes and plan for more effective intervention in classrooms, supported living settings, and work settings. It shows how to conduct a functional assessment and link assessment results to interventions, and provides an example of a completed functional analysis. An introductory chapter identifies fundamental assumptions of functional assessment. Chapter 2 discusses conducting a functional assessment, with sections on identifying, prioritizing, and defining problem behaviors; formulating hypotheses; and completing a functional analysis. Periodic self-check sub-sections are also provided. Chapter 3 is on linking assessment results to interventions. It covers selecting replacement behaviors, manipulating consequences, manipulating antecedents, and addressing setting events. Chapter 4 provides a detailed example of a completed functional assessment through the steps of identifying problem behaviors, prioritizing problem behaviors, defining problem behaviors, formulating hypotheses, and developing an intervention. The concluding chapter stresses application of an assessment process conducted through a combination of structured interviews, systematic observations, and functional analysis of problem behavior. (Contains 23 references.) (DB)