Whilst UK universities treat IELTS scores as proxies for readiness to participate in their programmes, a high IELTS score could obscure weak language skills in certain areas. This study explores the strength of the relationship between IELTS scores and receptive vocabulary size for a large sample of Chinese-speaking students on a pre-sessional course in the UK. Weaker correlations than expected were noted, meaning some students with low IELTS scores might have large vocabularies and vice-versa. This paper then focuses on a small group of students exploring how much coverage (percentage of words known) of reading texts from their destination degrees their receptive lexical knowledge is likely to provide. Textual coverage is modelled using the results of the vocabulary test and calculating the vocabulary profile (proportions of common and less common words) of a sample of the students’ semester one reading texts. It is noted that some students with strong IELTS scores may struggle to read in their discipline, based on this model.