English has been introduced as the medium of instruction in three-quarters of Master's-degree programs in the Netherlands and one-quarter of Bachelor's degree programs. The principal driving force behind this trend is internationalization, with the harmonization and Anglicization of higher education applied as means to that end. There is increasing criticism of this development within educational institutions and the Dutch House of Representatives. The main criterion is that the use of English should not undermine the quality of the education provided. The required level of proficiency in English for teaching and receiving academic education is C1 of the CEFR (Common European Framework of Reference). For native speakers of Dutch (L1), both verbal information processing and text production in English (L2) burden the working memory more than their own language would. Relatively little research has been conducted into the impact of English-medium instruction on the academic performance of Dutch students, and many of those studies that do exist are based on self-reporting rather than objective measurements. Semi-experimental research indicates that lecturers using L2 English are less clear, precise, redundant, and expressive, and also improvise less. Findings in respect of academic performance are inconsistent: some studies point to a decline, others find no effect on students' performance. Research into the impact of L2 as a medium of instruction is generally hindered by the non-random allocation of students to the language in which they are taught and a lack of objective measurements.