One of the most serious, but least examined, issues arising at the intersection of the 'new' genetics and public health is the relationship between social class and genetic burden. In the USA, concerns in ethics, policy and public discourses about genetic medicine and class structure have frequently been expressed in the notion of a potential 'genetic underclass'. The paper explores the usefulness of the genetic underclass metaphor for framing intersections of genetics and social disadvantage. Data are drawn from preliminary analysis of in-depth interviews with mothers of children affected with a genetic condition or illness, as part of a broader study of the state-funded Genetic Outreach Program serving rural Kentucky. The rst section of the paper brie y considers the notion of the genetic underclass as it has appeared in medical ethics and policy literatures. It is argued that the mechanisms of access and discrimination to which the genetic underclass concept is attached are not likely to be those through which the new genetics significantly reinforces or exacerbates social disadvantage. Little direct evidence currently exists to substantiate the notion of a genetically unemployable or uninsurable underclass. However, theoretical dimensions associated with the underclass as it appears in social strati cation literature do suggest ways of examining dynamics of genetic conditions and social disadvantage. In the second section of the paper, drawing from these dimensions and through cases analyses, issues and processes are identi ed that will be of importance to understanding relationships between social disadvantage and public health genetics.