Voluntary surveillance systems are subject to under-reporting.Figures may underestimate true numbers.Miscategorisation of probable country of infection by presuming the country with the highest prevalence as the likely country of infection will underestimate the number of infections acquired in the United Kingdom, particularly among people originating from countries with high prevalence.New HIV diagnoses do not represent new HIV infections, as diagnosis can occur at any point between infection and death, which in the natural course of infection is typically 10-12 years.Furthermore, surveillance reports do not distinguish between partners infected in high prevalence countries while visiting and partners infected before migrating from those countries.The number of people becoming infected with HIV through heterosexual intercourse in the United Kingdom is rising steadily.As the number of heterosexuals living with HIV (diagnosed and undiagnosed) in the United Kingdom grows, the likelihood of heterosexual transmission within the country will increase, particularly among ethnic minorities.The continuing collaboration of those who contribute to the voluntary HIV/AIDS reporting system in England, Wales and Northern Ireland is gratefully acknowledged, as is the help, advice, and support of Kevin Fenton (Health Protection Agency (HPA)), Noel Gill (HPA), Phillip Mortimer (HPA), Linda Lazarus (Department of Health), and Daniel Thomas (Communicable Disease Surveillance Centre Wales), and administrative support provided by Fay Peyman (HPA) and Fateha Begum (HPA).Contributors: VLG followed up reports.SD analysed surveillance data and wrote the first draft.VLG, SD, KS, and BGE were involved in the drafting of subsequent versions.BGE is guarantor