This study looks closely at the relation between background knowledge and L2 proficiency in L2 reading performance in two groups of university learners of English, one from Mainland China and one from Hong Kong. The students (n = 214) shared Chinese culture in general, but differed in terms of their local sub-cultural and social background. They were divided into intermediate and post-intermediate groups on the basis of a test of General Proficiency in English. Two English cloze tests were then constructed to assess reading comprehension, one with cultural content that would have been familiar to the Hong Kong students, and one that was culture free. The results show a strong cultural effect on reading comprehension, but not on post-intermediate readers. The findings have implications for teaching reading to L2 learners. [Copyright of Language, Culture and Curriculum is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/07908310308666657]