Philadelphia is one of several cities in the United States that has a disproportionately high rate of homeless adults. In 2009 the Office of Supportive Housing reported that on any given night, 6,304 people were homeless in the city of Philadelphia (Kligerman, Darling & Schaffer, 2010). Many of these homeless individuals have substance abuse or mental health issues. In the past the city has primarily used conventional methods to address this very serious problem, but recently efforts have been made to adopt an innovative method of housing for those who are considered chronically-homeless, the Housing First model. This paper will take a comparative look at the “Housing First” model, and the more traditional modality, commonly called “Continuum of Care”. The primary focus of this paper is to determine the effectiveness of the “Housing First” and “Harm Reduction” models on providing permanent supportive housing for homeless adults suffering with serious mental health and co-occurring substance abuse problems in the city of Philadelphia. This paper presents empirical evidence about the effectiveness of the overall services provided to the homeless population in Philadelphia, with a specific focus on Pathways to Housing, Philadelphia.