An aspect of assessment which has received little attention compared with perennial concerns, such as standards or reliability, is the role of judgment in marking. This paper explores marking as an act of judgment, paying particular attention to the nature of judgment and the processes involved. It brings together studies which have explored marking from a psychological perspective for the purpose of critical discussion of the light they shed on each other and on the practice of marking. Later stages speculate on recent developments in psychology and neuroscience which may cast further light on educational assessment.