This paper reports on the qualitative component of a mixed-methods study on unlinked anonymous testing for HIV in genitourinary medicine (GUM) clinics in two English cities. Unlinked anonymous testing is a system of monitoring population prevalence by testing residual blood samples taken for diagnostic purposes after they have been unlinked and anonymised from their source. Little is known about how individuals feel about their blood being tested in this way without their explicit consent, nor is it clear whether the process of unlinking blood affects how people feel about the use of their bodily material for public health surveillance purposes. We report participants' views on these issues, drawing on in-depth interviews with 20 GUM clinic users. The majority thought it preferable for blood samples to be used for population surveillance rather than being discarded. For most, blood and bodily tissue were not seen to represent personal identity even though participants understood that information about them could be gleaned from their analysis. The provision of information, rather than a strict consent process, was advocated as many felt that transactions between health professionals and patients should be as transparent as possible.