Abstract: The Unlinked Anonymous Prevalence Monitoring Programme began in 1988, and was aimed at measuring the distribution of infection, especially HIV, in accessible groups of the adult population. The programme provides estimates of HIV infection among groups in whom a substantial proportion of infections are undiagnosed and therefore not ascertained by other surveillance systems. Essential public health information on the prevalence of HIV infection in these groups cannot be obtained any other way. This report summarises programme data to the end of 2001.