Teachers say that they would gladly teach a day in the classroom if at the end of the day they could leave and have no marking. There is a common staffroom perception that mathematics teachers have it easy when it comes to marking. In arts subjects, setting an essay can be a fairly straightforward matter--a one-line question may suffice--but marking the completed essays is obviously time-consuming and difficult. The opposite is sometimes thought to be the case for mathematics: writing a mathematics examination takes a lot of time and care, but marking it can be fairly quick. People think that mathematics is always either right or wrong, so one can just tick or cross. In this article, the author explores the old problem of marking and how much time should be devoted to this task. He also challenges the mythology surrounding marking. (Contains 5 figures.)