HIV infection is associated with high treatment and care costs and subject to large differences in prevalence between health districts. Equitable distribution of resources requires information provided by an annual national survey of prevalent diagnosed HIV infections (SOPHID). This measures HIV caseloads by health district of residence throughout England, Wales, and Northern Ireland and is used to inform local public health professionals and to improve allocation of government funding for HIV prevention and care. Survey totals are adjusted by underreporting and non-attendance factors to produce a more accurate assessment of the total caseloads. On average the combined adjustments increase the reported caseload by 14.7% annually. Adjusted prevalence estimates ranged from 14,164 in 1995 to 18,460 in 1998, an increase of 30%.