Over the last several decades, the clinical prevalence of autism has increased considerably, as has the amount of popular and scientific attention directed towards the condition. However, discussions of autism tend to focus on children and finding a cause and a cure, while the growing numbers of adults diagnosed with autism have received relatively little attention. This dissertation begins with the argument that popular representations of autism are shaped by the idealism of modern medicine, and its overriding search to discover etiologies and treatments for all forms of biological difference that fall within its purview. And yet, for those responsible for adults with autism, management, care, and support are more relevant concerns to everyday experience than are cause and cure. In order to describe and analyze this everyday experience, this dissertation features a three-year ethnographic study of thirteen families with adult members with severe forms of autism. After reviewing pertinent historical and demographic information, the body of the manuscript explores: 1) the process by which caretakers negotiate between different definitions of problem behavior in the face of persistent situational complexity and ambiguity; 2) the contextual dynamics that make it possible for caretakers to perceive as innocent and/or humorous behaviors that are often viewed as atypical by others; and 3) the ways in which the experience of continued atypicality and dependency comes into conflict with popular representations of autism while at the same time highlighting the reality of the ever-looming future and the care and support required after primary caretakers are gone. At the end of the dissertation, I return to the argument that modern medical idealism discourages popular recognition that, in the case of autism, continued atypicality and dependency constitute the condition's usual prognosis. I conclude with a short consideration of how the themes explored in this thesis resonate with the experiences of those living with or alongside other forms of biological difference (e.g. disability, mental illness, Alzehemier's) that are currently incurable.