How we begin to serve others as healthcare professionals and how it is we define underserved and oppressed peoples is important in understanding issues in the organization and allocation of health care. This exploration, based on feminist post-structuralist theory, explores how nurses formulate definitions of 'underserved' and 'vulnerable'. This study goes beyond prescribed definitions to locate meanings used to identify oppression. I present, through an analysis of a literature search, the context and construction of the terms 'vulnerable population' and 'medically underserved'. Professional nursing journals are the source of relevant text. The implications of working with particular understandings of the terms 'vulnerable' and 'underserved' is based on my assumption that healthcare providers need to critically focus on the personal and political meanings they attribute to the labels used to define the clients and communities with whom they work. The presentation of this material supports that the way we define 'vulnerable' and 'underserved' is related to how our work fighting racism, ageism, AIDS, poverty, homophobia, addiction, domestic violence, sexism and colonization is realized.