A substantial proportion of HIV-infected individuals do not present for HIV testing until late in infection; these individuals are often ill, have a high mortality risk, and are less likely to respond to treatment when initiated. Furthermore, late presentation means that opportunities to reduce onward transmission, either by reducing high-risk behaviours or by reducing an individual's infectivity, are missed. The proportion of HIV-infected individuals who present late has remained relatively stable over the past decade, despite several attempts to encourage earlier diagnosis. Late presenters tend to be those at lower perceived risk of infection, those who are not routinely offered HIV testing, and are often from marginalized groups. Strategies that encourage earlier testing, including routine HIV testing in healthcare settings where high-risk individuals attend frequently, the availability of HIV testing services in non-medical settings, and partner notification schemes or peer-led projects to encourage high-risk individuals to attend for testing, may all increase the proportion of HIV-infected individuals who are aware of their HIV status, thus helping to control the spread of the epidemic. This review summarizes recent evidence on the epidemiology of late presentation and its impact on clinical progression, and describes several key strategies that may encourage earlier diagnosis.