Hyo Chang Hong. 2001. Referring Expressions of Late Old English: Discourse Functional Analysis of Apollonius of Tyre. Studies in Modern Grammar 25, 55-73. Old English referring expressions have mostly been dealt with in their sentence-internal grammatical functions. In this paper, I claim that, in addition to their case-marking functions, these referring expressions also played an important discourse-functional role in the development of Late Old English narratives. In particular, it is shown that Old English determiners sum and an, in conjunction with zero article, were major factors that determined the relative importance of the entities introduced by them.