This study aimed to answer the question of how many words of the Dutch language, and which words, an adult non-native speaker needs to know receptively in order to be able to understand first-year university reading materials In the first part of this study, an assessment was made of the representativeness of a list of 23,550 words (lemmas), taken from a school dictionary, for a 42 million-word token corpus of contemporary written Dutch It was found that, using frequency as a criterion, text coverage substantially increased with up to 11,123 words (i e words occurring more than 100 times in the corpus), but not beyond In the second part of the study, an assessment was made of the representativeness of the same list of 23,550 words for a relatively small corpus of first-year university reading materials The percentage of tokens covered in this small academic corpus did not differ substantially from the percentage of tokens covered in the big corpus analysed in the first part The third part of the study consisted of the development and administration of a 140-item multiple-choice vocabulary test aimed at measuring test takers' receptive knowledge of 18,615 content words of the 23,550 word list This test was administered to (i) native speakers entering university as freshmen, (u) non-native graduate students, and (m) non-native prospective students taking a Dutch language entry examination test battery Extrapolations of the test scores showed that the average vocabulary size of these three groups of test takers was 18,800, 15,800, and 11,200 respectively It is concluded that the minimal vocabulary size needed for university studies is 10,000 base words Earlier Dutch studies, suggesting that knowledge of 3,000 or 5,000 base words would suffice, appear to have underestimated such a minimal vocabulary 1