Success at university depends to a large extent on students' ability to read expository texts effectively in order to access and understand information, and study it for exam purposes. An important component of the comprehension process is the reader's ability to connect current information with information mentioned previously. One aspect of this text connecting process involves logical connectives. These are text devices that explicitly signal how chunks of information in a text are related to one another in a specific logical semantic relationship. This paper reports on findings from a study that investigated ESL students' ability to connect information linked by "illustrative," "causal" and "adversative" logical connectives during the reading of expository texts. The comprehension of logical relations was examined in relation to the students' academic performance and their language proficiency in English, the language of learning and teaching. The findings showed a robust relationship between the ability to comprehend logical relations in expository text on the one hand, and academic performance and ESL proficiency levels on the other hand. In particular, the academically poor performers found causal and adversative relations challenging. In discussing the results, the implications of these findings for reading comprehension in general and for academic support programmes for ESL students at tertiary level in particular are considered. (Contains 3 tables.)