This thesis examines the implementation of the CLIL approach in the Faculty of Medicine of the University of Colombo, Sri Lanka. The research idea sprang from a concern of the challenges and difficulties faced by students and language teachers with the recently introduced CLIL approach to English language programs in the Faculty of Medicine. The literature on CLIL, especially content- based language teaching, is reviewed and elements of best practice identified. A document analysis was conducted on the teaching resource used as the basis of an English course for medical students at the university. The analysis reveals several significant variations between the materials and the best practice advocated in the literature. These include a lack of balance between a focus on medical content and language learning, with an over-emphasis on the former. Visual presentations are not used in ways consistent with other approaches to CLIL and the range of text types dealt with is not extensive. The implications of these shortcomings are discussed and recommendations made. Implications for the application of CLIL are also briefly discussed.