In the past two decades, vocabulary researchers have determined the number of word families that an undergraduate needs to know in order to read effectively in English, and further work has examined vocabulary size among Indonesian university students. What this research has so far not considered, however, is the distinction in the learner's vocabulary knowledge between words of Germanic origin and words of Graeco-Latin origin, despite the importance of the latter in academic study. The question of the relative importance of the two vocabularies arose from a study of vocabulary size in the United Arab Emirates, a country in which English is a major lingua franca. Although the Emirati students knew many more word families than did their Indonesian counterparts, an examination of their test results revealed that they knew proportionately fewer of the important Graeco-Latin words than had been expected and were thus less well prepared for academic reading than their overall vocabulary size might have suggested. This paper describes the background to the study and presents the test results, and discusses the implications of the apparent bias towards words of Germanic origin. (Contains 7 tables.)