Framed in theories of social semiotics, this descriptive multiple case study examined six middle school teachers' use of gestures during one school year as they each taught two different subject areas: earth science, language arts, mathematics, and/or social studies. The data, which included field notes and photographs from 354 lessons and 151 video-recordings of lesson segments, were analyzed using constant comparative methods and multimodal concordance charts. The analyses indicated discipline-specific differences in types of gestures, frequency of gestures, and centrality of gestures to the teachers' messages. Earth science depended on a variety of iconic and deictic gestures, the latter of which was also common in mathematics. Communications in language arts and social studies commonly included non-essential action gestures that mimicked the movements of characters and historical figures. This study modifies existing claims of the importance of gestures in teaching, suggesting that gestures can play relatively central or minor roles in communicating disciplinary concepts. It concludes with implications for disciplinary literacy instruction that more rigorously accounts for the role that gestures play in disciplinary learning.