An exercise is described which aimed to make clear to first-year undergraduate medical students the expected writing skills required for an essay examination in one discipline. Many students were from a non-English speaking background and over one-third of students, regardless of language background, had limited experience in this type of essay writing. For this exercise, a practice essay was written by each student for formative assessment. The essay was rated by a tutor and by the student according to well-defined criteria. This allowed for comparisons to be made in a structured and objective way between the judgements of the student and the assessor. Students found the exercise to be very useful, although whether essay writing skills actually improved could not be established. Students from non-English speaking backgrounds tended to be most harsh in their self-evaluations, yet tutor-evaluations generally showed these students to have better writing skills than other students. Indeed, correlations between self- and tutor-evaluations were quite low. It is evident that students and their educators may be unclear about each others' expectations. By making explicit the requirements of an exercise, misunderstandings may be minimized and it is possible that student performance could improve, though further research is required to verify these hypotheses. It is suggested that students should be encouraged to evaluate their own work and should be instructed in writing skills throughout their medical degree education.