Understanding historical interpretation involves understanding how historical knowledge is constructed. How do sixth formers model historical epistemology? In this article Arthur Chapman examines a small sample of data relating to sixth form students' ideas about why historians construct differing interpretations of the past. He argues that understanding interpretation requires students to reflect on the decisions interpreters make, consciously or otherwise. Chapman highlights a tendency amongst the students in his sample to explain interpretation in terms of the identities of interpreters, rather than in terms of the logic of historical enquiry. Teaching about historical interpretation, Chapman concludes, must involve helping students to understand how disciplined historical enquiry works. (Contains 4 figures.)