Kiswahili is the African lingua franca of Tanzania. In the education system it serves as the language of instruction at primary school level. From secondary school and onwards, however the medium of instruction is English. This is an issue that has caused a lot of debate over the years. Many publications and a lot of research on the issue suggest that the current language policy is an obstacle to effective learning and teaching because students as well as lecturers are not sufficiently competent in English. Therefore it has been argued that the medium of instruction should be Kiswahili, also at post primary level.Although it seems obvious to many educationists that learners learn best through a language they understand well, there is also considerable support for retaining the English medium in Tanzania. The proponents of the English medium often argue that globalisation makes it important to keep the English medium, that the Kiswahili language lacks the necessary vocabulary to function as an academic language or that such a change is too costly for a developing country like Tanzania.The main objective of this study is to explore and gain insight into the various views concerning the medium of instruction at post-primary level in Tanzania with a special focus on higher education and the University of Dar es Salaam. The opinions of lecturers, professors and students were sought through open-ended interviews, employing the interview guide approach. The study also involved document analysis of Government policy documents, newspapers and earlier studies and publications on the issue.