||This research project departs form a sociocultural perspective on learning in general, and language learning in particular. It is focused on the development of shared understanding of task requirements by students working in pairs and the joint knowledge constructed through interaction within that process. In order to understand such a process a revision of several theoretical perspectives has been done. We consider language, consciousness and knowledge as social constructs, from which it follows the consideration of learning as a social phenomenon which occurs through interaction and scaffolding. This Sociocultural perspective, when applied to language learning, suggests the need for situated tasks that promote real interaction in engaging learning contexts. Also related with the Sociocultural Paradigm, we find the Activity Theory, that – in the context of language learning – analyses the learning processes as sets of goal-oriented activities, and the contextual elements that influence such processes. Activity Theory also suggests the need for relevant and meaningful learning contexts. At this point, we shall suggest Content and Language Integrated Learning (CLIL) as a methodology that meets all this requirements and promotes group and pair work, interactive activities and all the potential learning situations that interaction carries with it. From these viewpoints, the interaction in four pairs of students was analysed with the final objective to understand a little bit of the learning process, because “we must understand learning before we can teach. We can only study teaching in reference to learning, and we can only understand teaching if we understand learning” (van Lier, 1998: 130). The data was collected in a 2nd ESO inclusive classroom during the implementation of a CLIL didactic sequence on the Holocaust. The recording of 4 pairs were analysed, two of these pairs could be defined as symmetric and the other two as asymmetric. On analysing the data the focus was set on how a team of two students deloped a shared understanding of the requirements of a task, and with such objective in mind the following research question was posed: Do the students proceed according to instructions? What kinds of activities (as defined in Activity Theory ) do students carry out in order to develop a common understanding of what is expected from them? The answer to the first part of the question is “No”. The students had been given the written instructions, which had been read as a class (they had to write an article following several steps). The data confirmed that students do not strictly follow the instructions, however, from the Activity Theory perspective, they perform a wide range of goal-oriented activities which lead them to the final outcome (they do indeed write the article). From the analysis of the data from an emic perspective, several categories emerged: (1) Task management activities, among which negotiation of task meaning, negotiation of writing strategy, negotiation of roles, negotiation of general topic, negotiation of specific content, negotiation of setting, etc. (2) Evaluation of task (3) Encouragement (4) Doubts or hesitation (5) Self-repair (6)Elusion of responsibility (7) Off-task. Most of these activities imply some kind of negotiation which often brings joint construction of knowledge, that is, students learn while interacting. And the students not only learn language, but also content, and new ways of social communication. This research project has given us the chance to observe how the students develop a shared understanding, and thus learn together, eventhough they do not always proceed as instructed or asexpected. We should not then be discouraged when our instructions are not followed as planned, and make the most of the results from student negotiation.