This article explores the concept and role of intensity in the research project on Intensive Core French in the province of Newfoundland and Labrador. Intensity in this project is characterized by a reorganization of the timetable and a reorientation of the curriculum. The theoretical foundation of the project – a transdisciplinary approach to second language learning/teaching – is based on Cummins's hypothesis on the interdependence of languages, a sociopsychological theory of development, and Vygotsky's conception of the relationship between instruction and development. A model is developed in order to illustrate the relationship between second language learning and the development of cognitive, social and personal capacities and organizational skills. It is argued that the types of teaching strategies used in second language classrooms have important effects on the development of these capacities. The transdisciplinary approach developed in our research project, which tests on the concept of intensity and implies the compacting of the curriculum both in English and other subjects, enhances the effects of second language instruction.