The street youth of Montréal experience serious difficulty not only in identifying with the adult world, but also in occupying urban space without being able to establish themselves. Separated from traditional forms of social integration, these youth attempt to institute, in a precarious manner, a certain use of the urban socio-spatial margin with a view to reconstructing identity. This socio-spatial margin is presented as a geographical organization, structuring topologically the practices of spatial appropriation and social identification. The author thereby invites us to understand theoretically the link between the identification process and a heterogeneous representation of space. It is through the key concepts of transitional space (winnicottian psychoanalysis) and geographical trajectory (structural geography) that it would be possible to identify a geo-social path of street youth, beginning with running away. In order to evaluate the potential for marginalized socialization of street youth, this path is placed in relation to certain elements of urban use management, such as programming, accessibility, control and surveillance.