The cervical screening programme has prevented many thousands of cancer deaths in the UK, say researchers.
Smears can pick up cellular abnormalities
Experts believe that 15 years ago it was heading for a devastating outbreak of cervical cancer among women born between 1951 and 1970.
However, they estimate that systematic cervical screening, introduced in 1988, is now preventing up to 5,000 deaths a year.
The study, by Cancer Research UK, is published in The Lancet.
The death rate from cervical cancer increased threefold from 1967 to 1987 in women aged under 35.
However, since the national screening programme began in 1988 the trend has been reversed.
Lead researcher Professor Julian Peto said changes in sexual behaviour since the 1960s led to epidemic levels of sexually transmitted diseases.
This in turn meant that HPV (human papillomavirus) infection became increasingly common among sexually active women.
Some forms of the virus only cause genital warts, but others cause cervical cancer.
Up to half of the young women in Britain have been infected with a high-risk strain of HPV by the time they are 30.
However, although HPV infection affects many young women, regular cervical screening is able to pick up abnormalities and treat them quickly before cancer develops.
Professor Peto said: "The cervical screening programme will prevent about 5,000 future deaths each year in Britain at a cost per life saved of less than £40,000, or about £2,000 per year of extra life.
"Despite occasional but widely publicised failures the British cervical screening programme is already remarkably successful and is still improving."
Professor Peto's research compared falling death rates from cervical cancer since 1988 against the projected increase if screening had not been introduced.
The researchers also compared data from other countries. Before the screening programme was introduced, the death rate from cervical cancer among British women aged under 35 was among the highest in the developed world.
Only Bulgaria, Hungary and Romania had higher rates than the UK.
Julietta Patnick, director of the NHS Cancer Screening Programmes, said: "I am delighted that these findings recognise the huge contribution that the cervical screening programme has made to saving women's lives.
"As this research shows, regular screening is one of the best defences against cervical cancer and so I urge all women to attend when invited."
Around 3,000 new cases of cervical cancer are diagnosed in the UK each year. It can affect women of any age who are, or once were, sexually active.
Scientists have linked nearly all cases of cervical cancer to HPV.