This paper reports findings from a study on the discourse functions of basic "wh"-clefts such as "what our brains do is complicated information processing" in 160 lectures drawn from the British Academic Spoken English (BASE) corpus. Like much linguistic research on this academic genre, the investigation is motivated by the need to gain a better understanding of language use in lectures to aid effective English for Academic Purposes (EAP) course design. To this end, the composition of the "wh"-clauses was analysed for its main constituents (subjects, verb phrases and modality) and the clefts were grouped according to their apparent main function and subfunction within the lecture discourse. The results show that basic "wh"-clefts mostly serve to highlight aspects of content information and there was also disciplinary variation in their use. Implications for EAP course design are discussed. (Contains 3 figures and 6 tables.)