This article considers the NHS cervical screening program and the controversies which have attended the introduction of comprehensive screening in a partially screened population of women in whom the underlying risk of disease was unknown. The increase in screening coverage which has taken place since 1988 has coincided with a period of high prevalence of cervical cancer and its precursors among women in the screening age group, against which background the recent fall in mortality and incidence of the disease has been a far greater achievement than generally recognized. The success of the program is considered in the context of the expectations and limitations of the test itself, and the high standards required for screening to be effective.