This article describes the development and initial implementation of the Comprehension and Learning from Text Survey (CoLTS), an instrument designed to assess teachers' specialized knowledge for comprehension instruction in the context of discussion. CoLTS is a paper-and-pencil test that engages teachers in analyzing a text to identify the most important ideas, as well as those text features that might challenge readers' comprehension. Teachers are also asked to respond to scenarios of teacher-student dialogue about the text in order to reveal (a) their analysis of student responses to questions and comments about the text and (b) their understanding of specific discourse moves designed to engage students in making sense of text ideas. Analysis of teacher responses to the CoLTS tasks provides important information for those who work with teachers to develop their understanding about how to support student comprehension in text-based discussions. (Contains 4 tables.)