Despite the existence of an effective screening technique for cancer of the cervix, incidence and mortality from this disease have not declined in the United Kingdom. The basic problem is that women most at risk of the disease are under-represented in the screened population. The evidence for two different points of view to explain this situation is examined. These viewpoints are the failure of the women to attend, and the failure of the service to meet the needs of women. This paper argues that the evidence supports the view that the organisation of the existing screening service impedes the maximum participation of at-risk women. We discuss the features that an effective service needs to incorporate, and put forward principles for the development of a more effective screening system, namely, that it should be provider-initiated and user-oriented.