As we begin to apply functional assessment procedures in mainstream educational settings, there is a need to explore options for identifying behavior function that are not only effective but efficient and practical for school personnel to employ. Attempts to simplify the functional assessment process are evidenced by the development of informant assessment measures (e.g., interviews, rating scales). In this study, the agreement (i.e., on relative rankings and primary function) across sources of information regarding behavior function was examined for 19 students in a middle school setting. These measures included teacher ratings, student ratings, student interviews, observer ratings, and conditional probabilities. In addition, for 1 student, whether information obtained through these sources was consistent with that obtained through a brief analog analysis of function was examined. Results indicated low agreement regarding rank order of behavior function and on primary function across all sources of information.