The study seeks to establish whether the institution has achieved permanent changes in the youths treated and what treatment techniques have brought about changes. Psychologically trained educators work with groups of 12 to 15 juveniles using pragmatism, support, group cohesion, and personal relationships with individual youths to encourage clients' participation in reeducation activities. The social climate of the institution is characterized by coherence and efficiency, supportive educator influence, and intense client participation. Juvenile delinquents selected for Boscoville are considered especially dangerous because of their relatively advanced age and the nature of their offenses. Only 19.3 percent complete their reeducation; successful program participants tend to have higher IQ's to be more articulate, and to have a less developed criminal identity than those who quit. The institution applies the theory of rehabilitation through stages, i.e., acclimatization, control (goal achievement), production (creativity development), and personality development (autonomous and harmonious living). Each stage is subdivided into beginning, organization, and consolidation phases. Transverse and longitudinal evaluation of two groups of residents (61 and 116 subjects) suggests that substantial changes take place in delinquents treated for more than a year. Levels of aggression and antisocial behavior are reduced, with less marked but clear improvements in adaptation and integration. Results are uncertain for depression, neuroses, and defensiveness. The Boscoville program actually appears to contribute to the psychosocial maturation of juvenile delinquents and to assist in their personal development. A 37-item bibliography, graphs, and tables are supplied. --in French.