The purpose of this paper is to introduce ecological momentary assessment (EMA) as an effective approach for capturing teachers' emotional states and behaviours over time. Although the implementation of EMA has a rich and successful history among social science researchers in general, traditional retrospective, self-report methods for collecting teacher and teaching data remain the norm within the field of education today. This paper addresses this concern by describing the conceptual and methodological background of EMA, using methodological findings from a recent study of middle school teachers as a practical example. Results indicated that the advantages inherent in EMA research with teachers clearly outweigh the drawbacks. Teachers and researchers alike felt that the use of EMA via the handheld instruments of personal digital assistants (PDAs) yield meaningful within-person data in an accurate and convenient manner. Based on the lessons learned from this study, future considerations are outlined for the incorporation of EMA methods via PDAs with teachers. (Contains 4 tables and 4 notes.)