The introduction of colposcopy and exfoliative cytology as a means of examining the cervix uteri has opened up the possibility of studying the preceding and early stages of invasive carcinoma of the cervix and has also brought to light a number of conditions which are possibly only indirectly related, if related at all, to cervical neo- with histological evaluation it is possible to plasia. Using these methods combined gain some insight into the natural history of cervical carcinoma. The importance of this is not confined to the cervix for, in this respect, the cervical lesions may prove a paradigm for those of the bladder, stomach and elsewhere. At present the broad outline of the natural history of these cervical lesions is emerging but the temporal and spatial relationships of the various phases is unclear, largely because of the number of possibilities envisaged which involves more vari- ables than can be controlled in anyone investigation. In this monograph we have endeavoured to indicate the limitations of the various approaches and to stress the need for controlling the accuracy of assessment whether it be histological, cytological or colposcopic.