Part of a review symposium on a book by John Hagan & Bill McCarthy, Mean Streets: Youth Crime and Homelessness, (Cambridge: Cambridge U Press, 1997). This work, based on 10 years of research in Toronto, Ontario, & Vancouver, British Columbia, offers a life course perspective on the social problem of homeless juvenile delinquents & criminals. The book's objectives, design, & theoretical orientation are reviewed, offering a comparison to the ideas of W. I. Thomas on environmental change & life-shaping experiences.