The internet is now a major source of health information for lay people. Within the medical, sociological and popular literatures there have been three main responses to this development. We classify these as ‘celebratory’, ‘concerned’ and ‘contingent’. This paper falls into the third category and, drawing on techniques of discourse analysis, examines people's accounts of their use of online health resources. It identifies six implicit rules – which we call ‘rhetorics of reliability’– that people readily draw upon when articulating why they trust some online sources and not others. In addition participants locate their accounts within broader discursive frameworks in order to present themselves as ‘sensible’ users. The article concludes by suggesting that there is an emerging concordance between the lay use of the internet for health and illness and dominant (generally) biomedical conceptions of what constitutes ‘good quality’ health information.