Abstract This chapter revisits Tyler’s early research on ITA comprehensibility while also considering recent work on instructional discourse. The purpose of the study is to explore Tyler’s early conclusions regarding the sources of listeners’ perception of incoherence in ITA classroom discourse. Following Tyler’s methodology, the data collected consists of videotapes of the same lab session taught by four different TAs, two native speakers and two non-native speakers. The transcripts of the lab sessions are analyzed in terms of the use of discourse management strategies to determine the differences between native speaker and non-native speaker TAs. Finally, we discuss how those differences may affect ITA comprehensibility as well as implications for ITA training.