While research into classroom language assessment has expanded in recent years, the nature of thought processes used by teachers when conducting such assessment has received less attention. This article reports on research that explored these cognitions through case studies of two instructors teaching an EAP (English for Academic Purposes) course in a UK university language center; data collection involved classroom observations, interviews, and stimulated recalls. This paper describes the numerous types of cognitions that the study found teachers drew upon when assessing students. Based upon these findings, the paper also suggests ways for improving classroom assessment, highlights the influence of managerialism, and considers the social construction of student language ability in the classroom. (Contains 6 footnotes and 1 table.)