This paper contributes to the literature on patients' claims-making work by analysing the epistemological strategies and standards used by members of an endometriosis patient community. It draws upon focus group research with members of a support group for endometriosis sufferers, and an open-ended survey of an e-mail list for women with the disease. Lynn Hankinson Nelson's (1993) concept of epistemological community is used to examine standards and practices for developing and evaluating knowledge used by women with endometriosis. Particular attention is paid to the use and centrality of the notion of experience within this community.