A small number of UK nationals who have a low, unrecognised or unacknowledged risk for HIV present late in the course of HIV infection; often after frequent attendances to primary care physicians. Information from in-depth interviews with individuals diagnosed with HIV in England, Wales and Northern Ireland (EW&NI) was analysed. Those diagnosed because of HIV-related symptoms (late diagnoses) were compared with those diagnosed for other reasons. Of the 286 individuals interviewed, 157 (55%) had HIV-related symptoms at the time of diagnosis, and 129 were tested for other reasons. A greater proportion of those diagnosed late were male and older. Of the 157 late diagnoses, 77 were considered to have acquired HIV heterosexually in the UK, 19 heterosexually abroad, 16 through 'high-risk' behaviours, 15 heterosexually by a 'high-risk' partner, four through blood transfusion and the remainder through an unusual or unknown route. A significantly higher proportion of those diagnosed late had had a long-standing relationship. None had been informed by a current or ex-partner of their HIV status. Primary care physicians should consider HIV as a possibility when patients without an apparent risk for HIV-infection present with symptoms indicative of possible immune suppression. Sensitive partner notification practices that enable a greater number of individuals to inform their partners should be explored.