The importance and amount of English as a Lingua Franca (ELF) usage and English Medium Instruction (EMI) lectures continue to increase on university campuses as universities worldwide seek to promote internationalization among both the student body and the faculty. While EMI has become a priority, the teaching and learning that occurs within this framework needs to be monitored for effectiveness and efficiency. Many of the teachers and students in these EMI courses do not share a common first language and likely have a first language other than English. Therefore, they are operating in EMI with varying levels of second language (L2) English ability, which can lead to low levels of student comprehension, learning and satisfaction unless the lecturer takes special care in their delivery of content. This paper explores the linguistic composition of EMI lectures in the Swedish context and reports survey findings of students' self-reported levels of comprehension related to lecture content and their lecturer's L2 English use. Three case studies are described and illustrate various linguistic factors that can contribute to or inhibit student comprehension in EMI lectures. Pedagogic implications are presented with the intention of supporting EMI lecturers and their students.