Acute human immunodeficiency virus (HIV) infection (AHI) can be defined as the time from HIV acquisition until seroconversion. Incident HIV infection is less well defined but comprises the time from the acquisition of HIV (acute infection) through seroconversion (early or primary HIV infection) and the following months until infection has been well established, as characterized by a stable HIV viral load (viral load set point) and evolution of antibodies with increased concentration and affinity for HIV antigens. During AHI, a viral latent pool reservoir develops, the immune system suffers irreparable damage, and the infected (often unsuspecting) host may be most contagious. It has proved very difficult to find individuals with AHI either in longitudinal cohorts of subjects at high risk for acquiring the virus or through cross-sectional screening, and the opportunity for diagnosis is generally missed during this phase. We review the technical strategies for identifying individuals with acute or incident HIV infection. We conclude that further technical advances are essential to allow more widespread detection of patients with AHI and to affect HIV treatment outcomes and transmission prevention.