An analysis of interrater agreement across multiple respondents on two anecdotal assessments, the Motivation Assessment Scale (MAS) and the Functional Analysis Screening Tool (FAST), was completed for an individual who displayed aggressive behavior. The results of the assessments indicated high agreement across assessments and respondents that the problem behavior was maintained by social positive reinforcement in the form of contingent delivery of tangible items. By contrast, a subsequent experimental analysis indicated that the behavior was maintained by escape from demands. A treatment was implemented based on the functional analysis outcomes to determine if the functional analysis had correctly identified the maintaining variable of the aberrant behavior. Results of the treatment analysis showed significant reductions in the occurrence of aberrant behavior suggesting that the MAS and FAST may not have accurately identified the maintaining variable of the aberrant behavior.