Given the importance of the ability to use variables flexibly in Calculus and students' difficulties related to various uses of variables, this study examined how variables are treated in calculus class. Data for this study came from graduate teaching assistants' (TAs') classroom teaching, which plays a crucial role in undergraduate students' learning of entry-level mathematics, but of which we still have a limited understanding. We analyzed TAs' uses of variables in terms of prior literature examining how students use variables and what uses of variables cause difficulties for students. Our results show that the uses of variables by the TAs in this study typically aligned with students' dominant conception of variables as symbols to be manipulated and did not give students many opportunities to consider the uses of variables that commonly cause difficulties for students.