Scientific argumentation is increasingly seen as a key inquiry practice for students in science classrooms. This is a complex practice that entails three overlapping, instructional goals: Participants "articulate their understandings" and work to "persuade others of those understandings" in order to "make sense of the phenomenon under study" (L. K. Berland & B. J. Reiser, 2009). This study examines the argumentative discussions that emerged in two middle school science classrooms to explore variation in how the goals of sensemaking and persuasion were taken up. Our analyses reveals that each classroom engaged with these two goals but that they did so quite differently. These differences suggest that the students in each class had overlapping but different interpretations of argumentation. In addition, comparing across the class' arguments suggests these two goals of scientific argumentation may be in tension with one another. (Contains 7 tables and 3 figures.)