Over the last ten years, the homelessness phenomenon has been characterized by the growth of a particular segment, often designated by the expression "street youth" (jeunes de la rue). This article reviews the literature pertaining to the difficulties and debates surrounding the definition of the youth homelessness phenomenon. A general portrait of research trends and issues is given through the examination of theoretical orientations, research methodologies and the definitions of the terms "homeless" and "youth." It is on the basis of the diversity of these problematic elements that the proliferation of research avenues into this new social phenomenon can be understood.