In this study we investigated associations between studying in a foreign language and students' academic achievement and study behaviour. Data were gathered in the Netherlands, at the Delft University of Technology (DUT). The results show that the success rate of foreign students was about the same as that of the Dutch students, but that foreign students needed more time to pass the examination. Language proficiency played a major part in explaining differences in study achievement as did the presence or absence of a selection procedure in the student's country of origin. Furthermore, the results show that the study behaviour of foreign students was significantly different from the Dutch students: their average grades on examinations were lower, they made more attempts before passing an examination, they were more likely to postpone examinations and to follow a different order from the recommended one. Suggested measures to improve foreign students' study success include requiring higher levels of language proficiency and stricter selection of foreign students in the country of origin. It is suggested that a system of mentors which provides for intensive coaching of foreign students in their first year may prevent a slow start.