In the UK, over 70% of AIDS, including new cases, is located in a few Districts in central London where the distribution of previously occurring and new cases is essentially confined to the original risk groups of homosexual/bisexual men, drug addicts of both sexes, and some of their sexual partners and consorts. But control policy is still based on the assumption that HIV has already spread from persons in these risk groups into the general population, and that it will spread hereafter at an increased rate because of heterosexual transmission to cause a widespread epidemic of AIDS. The basis and implications of this policy were investigated in the South East region adjacent to London. Analysis of demographic and epidemiological data shows that, with one exception, there is very little extension of AIDS from affected Districts in London to the surrounding region or even to the suburban fringe. Where AIDS is prevalent, as in this exception, the distribution follows the same, original pattern which relates essentially to risks arising from life-styles. There is no significant association between the prevalence or spread of AIDS and conventional markers of deprivation, economic and social disadvantage. Allocations of personnel, services and expenditure, assessed from returns required under the AIDS Control Act of 1987 and official registration data, continue to follow the original policy assumptions. They are therefore unrelated to the numbers of existing and new cases, disproportionate and unrealistic. Claims that this widespread excess of effort is justified by the fact that AIDS has not spread to the general population are falsified by the continuation of cases almost exclusively in risk groups. There is nothing in the data required under the Act or in registrations in this main locus of AIDS in the UK to suggest any change in this or to justify continuation of current expenditure and redundant activities. There is no evidence in these data that ethnic variations in the resident populations of Districts are associated with variations in the prevalence of AIDS. However, the larger figures available in some of the national data do indicate a disproportionate increase in some minority ethnic groups. Further detail about risks factors in these groups are required and, meanwhile, effort and expenditure should be re-orientated toward treatment, contact tracing and other public health measures for more effective containment of the continuing spread of AIDS in all the high risk groups.