According to the behavioural approach, man is the product of his interaction with the environment. Normal as well as pathological behaviours are seen as the result of learning. Even individual subjectivity is perceived as a collection of internal behaviours responding to the same laws as overt behaviour. The therapeutic intervention consists therefore in the restructuring of learning conditions so as to eliminate problem behaviours from the individual's repertoire, and to replace them with more adapted behaviours. The approach does not, however, provide a definition of adaptation. The latter is a value judgement, made by society or the interventive agent, with respect to the individual's behaviour. Serious ethical problems can be posed and the interventive agent must take them into consideration. At the level of intervention in community health the behavioural approach suggests the use of milieu ressources to settle individual problems. Therefore the consultant becomes an educator and a planner in resource-utilization rather than a "therapist" in the traditional sense of the term» This approach provides very powerful methods of action at the level of primary and tertiary prevention and of evaluation of interventive success.