The majority of those infected and affected by HIV are younger adults. The ability of highly active antiretroviral therapies (HAART) to extend survival means that those infected when younger may reach older age, and future increases in numbers of older individuals living with HIV in England, Wales and Northern Ireland (E,W&NI) are expected. Evidence that older individuals engage in risky sexual behaviours suggests potential for HIV transmission. Data from national HIV/AIDS surveillance systems were reviewed (1997-2001). An older individual is defined as aged 45 years or over. Between 1997 and 2001, 2290 older individuals were diagnosed with HIV; 361 in 1997, rising to 648 in 2001. Heterosexual acquisition accounted for 1073 (47%) infections; 662 were male. Where reported, 666 (65%) older heterosexuals were probably infected in Africa, 144 (14%) in the United Kingdom and 113 (11%) in Asia. There were 1020 (45%) new diagnoses acquired homosexually; white (92%), infected in the United Kingdom (78%). Numbers of older individuals accessing HIV-related services more than doubled between 1997 (2488) and 2001 (5175). In 2001, 2270 (53%) were London residents. Between 1997 and 2001, among HIV-infected older individuals attending genitourinary medicine (GUM) clinics, the proportions previously undiagnosed were 60% and 82% in heterosexual males and females respectively, and for men who have sex with men (MSM), 42%. Numbers of older individuals newly diagnosed with HIV have increased in recent years. The increase in numbers of older individuals accessing HIV-related services were in excess of younger adults. A significant proportion of older HIV-infected female heterosexuals and MSM were undiagnosed. Awareness must be raised among clinicians, and an 'aged response' to HIV is required.