While traditionally self assessment has not been part of courses, it has had an important role in learning. Students are always self assessing. Before they hand in an essay or report, many have formed some notion of how good they think the piece of work is. Language students have routinely tested themselves on lists of vocabulary, medical students have traditionally closed their anatomy books and drawn diagrams to check their understanding, mathematics textbooks have provided examples for students to try out and given answers for students to check their calculations at the back of the book. In open learning materials, in-text questions have encouraged students to think about and check their learning. All of these are examples of ways in which students have traditionally tested their academic discipline knowledge and skills: what they know and what they can do. Although this kind of self assessment is ad hoc and appears peripheral to formal assessment procedures, it is a commonplace part of learning. There are good reasons, as we shall later see, for treating it more consciously and systematically.