The French obligatory prenuptial certificate is issued by a doctor in the light of certain examination results. The medical consultation which it implies offers a special opportunity to obtain from women a cervical smear that would allow the finding of possible pre-cancerous lesions of the uterine cervix. Such smears, along with supervision or treatment of the lesions discovered would amount to genuine prevention of cervical cancer. The evaluation made in this article shows that, among 370,000 women, it would be possible to find 5,800 dysplasias and 2,400 in situ cancers each year. This form of prevention would give 165,000 extra years of life and would economise treatment costs amounts to 250 millions francs, whereas the smears taken at prenuptial examination would cost 30 millions francs.