Using data collected by Project Renewal's mobile medical services to homeless people in New York City, this paper discusses a tension between an emergency medicine model of outreach and that of primary care. In the former model, clinicians evaluate clients on the basis of presenting complaints and refer them, as necessary, for specialized treatment. The latter is a broader model of comprehensive outreach and/or treatment, where clinicians screen clients and assess them for various conditions offering ongoing evaluation and treatment on site. The model of outreach is applicable for some homeless clients, but the prevalence and overlap of physical complaints, infectious diseases, substance abuse, and psychiatric symptoms among homeless people in New York City has resulted in an evolution toward broader approaches to outreach in this population. Improvements in diagnostic testing and increasingly portable medical technology may make the mobile delivery of medical care to homeless persons increasingly feasible.