In recent years, there has been an increasing emphasis on the use of functional assessment (FA) in the selection of treatments for problem behaviors. Scholars now generally accept that an understanding of the antecedents and consequences of problem behavior, achieved through a FA, is necessary to select the most effective treatment procedure. Yet, there are still a number of unanswered basic and applied research questions about such assessment procedures, such as how to identify the most effective and most efficient strategies for obtaining valid and accurate assessment data. To shed light on these issues, this study compared the results of functional analysis manipulations and more indirect, less intrusive methods. A second question of importance related to the utility of functional analysis results, particularly the manipulations, on different populations in applied settings. This study examined 20 students between the ages of eight and 12 who were identified as having an emotional disability according to the state's law. The researcher asked the students' teachers and classroom paraprofessionals to complete questionnaires and interviews. The researcher then made classroom observations, conducted student interviews, and completed functional analyses that manipulated potential functions or categories of maintaining reinforcers. The researcher analyzed the results comparatively. The data indicated that, although there is some agreement within certain categories of assessment methods, the indirect methods generally had poor agreement with the results of the functional analysis. From a more global perspective however, this study identified that the behaviors associated with students with E/BD were maintained by escaping followed by gaining attention. Behaviors maintained by gaining a tangible or sensory stimulation were rarely identified. Although there is growing pressure on educational practitioners to conduct efficient and effective functional assessments, the results of this study provide little direction for identifying an agreed-upon, user-friendly FA method whose results mirror those defined by the more rigorous functional analysis. Clearly, as FAs become more of a basic and necessary component in the development of effective educational plans, it is crucial for researchers and practitioners to investigate and identify agreed-upon, user-friendly, and effective assessment methods and strategies. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]