This paper reviews existing literature on the homeless population worldwide, with a particular focus on research conducted in the UK, in order to identify who the homeless are in the UK and what provisions exist for them in current government policies and initiatives. It begins by reviewing studies that attempt to identify risk factors for homelessness. Risk factors are discussed through macro (economic) and micro (individual) level concepts and the role they have in both causing and maintaining homelessness. Current estimates of mental illness among the homeless are reviewed as well as the effect of resettlement on mental illness. The paper then focuses on pathways into homelessness, paying particular attention to the relationship between trauma, personality disorder and coping styles within the homeless population and the specific role that some coping behaviours have in chronic homelessness. Literature is examined from the fields of mental health, personality disorder and coping conducted with general, psychiatric, and homeless populations and explores the complex relationship between individual risk factors, personality disorders and subsequent coping behaviours, in an attempt to understand the contribution they have to the process of becoming and remaining homeless. Finally, the paper examines existing models that have attempted to incorporate risk factors in explaining pathways to homelessness and concludes by hypothesising a model that includes both personality disorder characteristics and coping behaviours in perpetuating homelessness. The paper concludes by discussing future directions for research among this vulnerable population.