HIV infection is increasingly common in the elderly. This population is a heterogeneous group with particular epidemiologic characteristics and often with associated comorbidities, which frequently delay diagnosis and lead to poor immunological status at the start of highly active antiretroviral therapy (HAART). There are no differences between elderly and young HIV infected patients in the recommended antiretroviral regimens. Tolerance to treatment is good and the virological and immunological response to HAART is positive, although immunological response is slower and lower than in younger patients. Treatment adherence, which has been shown to be the only protective independent factor related to virological failure, is better in the elderly.