The field of sex work and sex trafficking is a highly contentious one, and organizations that represent sex workers have different conceptions as to what solution best serves this population. In Chicago, as in many major cities across the US, there are several groups that pose what they believe are viable solutions to problems related to sex work. One group advocates for an “abolitionist” approach, meaning that they advocate for abolishing the sex trade, through service provision for victims of prostitution and increased criminalization and fines for purchasers of sexual services. In Chicago, this group is referred to as “End Demand,” a group of individuals and organizations that have formed a large advocacy coalition to lobby for changes in prostitution laws. As their approach has been institutionalized in law enforcement and service provision, I refer to them as the incumbent organization in this field. Another group advocates for the complete decriminalization of sex work (for buyer and seller), and the acceptance of sex work as a type of labor. This group does not consider sex work a problem in and of itself, but rather suffering from problems stemming from illegality and stigma. While there are several organizations that acknowledge this decriminalization approach, the most prominent one in Chicago is the Sex Workers Outreach Project (SWOP-Chicago), a small, volunteer and sex-worker run organization that provides peer support and small scale human services to sex workers. SWOP-Chicago is the challenger organization, seeking to provide an alternative to End Demand approaches to sex work. Both of these groups collaborate with human service nonprofits that work with sex workers in order to disseminate their preferred service approach with this population. This dissertation examines the Chicago-based field of sex work and sex trafficking through the lens of these advocacy organizations that claim to represent sex workers, as well as human service nonprofits that may provide services to this population. This dissertation seeks to answer three central questions. First, how are human service nonprofits, those organizations tasked with providing services to sex workers, situating themselves in this debate around sex work? Second, how is SWOP-Chicago, the challenger organization, working to gain allies in the human service nonprofit field in order to counter discourse put out by the incumbent? Third, how are human service nonprofits collaborating with advocacy groups (End Demand and SWOP-Chicago) to address the concerns that they feel are impacting sex workers? Data for this fourteen-month project was gathered through approximately 500 hours of participant observation of SWOP-Chicago, as well as observations of events (conferences, panels, theater performances, fundraisers, etc.) that referenced issues of sex work and sex trafficking in Chicago. I also conducted a total of 53 interviews with players in this field: nine interviews with board members of SWOP-Chicago, four interviews with End Demand advocacy organizations, thirty-eight interviews with high level employees of human service nonprofits, and two interviews with employees at government organizations. In this analysis, I also included a document review of news and media articles that discuss issues of sex work and sex trafficking in a national context. I use the theoretical frameworks of Strategic Action Fields (SAFs) and institutional logics to situate my findings. I found that although there are a few nonprofit organizations that continue to support the End Demand approach, many human service nonprofit respondents (as well as the government respondents) are beginning to question the predominance of the End Demand logic, for three major reasons. First, respondents are concerned that End Demand may increase, rather than decrease criminalization of their clients. Second, is the growing popularity of harm reduction logics to working with individuals that may be engaged in “risky” behaviors such as sex work and drug use. Harm reduction, with its focus on behavior reduction rather than abstinence aligns more with decriminalization logics to sex work. Third, are the increased efforts among SWOP-Chicago, the “challengers” in this study, to promote their approach to sex work to human service nonprofits across Chicago—in the past several years they have provided workshops and trainings for a number of service nonprofits across Chicago, almost all of whom have responded positively to SWOP’s presence in their institutional field. However, although some organizations have been supportive of SWOP, very few organizations have been willing to publicly come out as supporters of the decriminalization of sex work, even if individual staff members may privately support decriminalization. Broadly, this study adds to our knowledge of how advocacy organizations collaborate with human service nonprofits and what this actually means for the population of concern. More specifically, I contribute to our knowledge of understanding how human service nonprofits, many of whom do not serve specifically serve sex workers, situate themselves between these mutually exclusive logics of abolitionism and decriminalization of sex work. Social work, and by extension human service provision, has been historically associated with treating sex workers as victims, and trying to abolish the sex industry. This project demonstrates that there are social workers and human service providers that are taking the uphill climb in challenging this discourse with the assistance of SWOP-Chicago.