This study explores the dynamic combination of structural factors domestic conditions, individual and social characteristics, and personal choices that produced episodes of homelessness among a representative sample of young adults (aged 20 to 45) in the city of Philadelphia in the late 1980s. Forty-three single adult homeless people (31 men and 12 women) were selected from a variety of shelter and nonshelter locations and interviewed in-depth about their experiences of becoming homeless. Statistics describing the residential transitions of the survey participants and a weighted distribution of the casual factors of their homelessness revealed the major significance of family relations, work and income, drugs (abuse, dealing, and environment), disabilities and previous institutional experiences. On the basis of written transcripts, combinations of these contributing factors have been identified. Interview selections are provided to illustrate these combinations, or the dynamic "pathways to homelessness" and the active decision-making processes of the participants. The study findings are interpreted as showing that, considered independently, neither reductionist models of homelessness that emphasize the causal influence of deviant behavior (primarily mental illness and substance abuse), nor the deterministic models of homelessness that examine structural factors independent of their biographical mediation (such as the housing and income crises), are sufficient for understanding the complex relationships that produce episodes of homelessness. While historical, social and economic factors determine the extent and demographic distribution of residential instability in the population, the mediation of those factors in the domestic conditions, personal experiences and restricted choices of men and women is critical to understanding how people become homeless. This study includes a chapter examining the historical, social and economic contexts of residential instability among young adults in Philadelphia.