After the harmonization process carried out in Spanish higher education following the Bologna Declaration, many universities have decided to introduce English as the language of instruction for some studies. From 2010, the new study programmes have been implemented, and there is an urgency to define what is meant by "teaching in English". Some researchers have investigated the constraints and difficulties of introducing a second or third language of instruction and have shown the difficulties content teachers have in recognising and describing their disciplinary discourse (Jacobs, 2007), which would make it very difficult for them to teach it in a foreign language. There seems to be a need for dialogue between language and content teachers, in which they can express their experiences, opinions and fears. An innovative education project proposed by ESP teachers at Universitat Jaume I investigated how teachers intend to implement the directive to introduce English as a third language of instruction and the relationship they think should be established between language and content teachers. This paper summarizes the discussions developed in the meetings held in the framework of this project.