The method entails making a visual inspection of the cervix, using a speculum (a tool to dilate the vaginal walls), a bright halogen lamp and a solution of three- to five-percent acetic acid.
The solution is applied to the cervix, and suspect tissue shows up as whitish lesions. Healthy tissue shows no colour change.
Doctors led by Rengaswamy Sankaranarayanan of the International Agency for Research on Cancer (IARC) in Lyon, France, tested the method on 31,000 women aged 30-59 in the district of Dindigul, in the southern state of Tamil Nadu.
A total of 3,088 women were screened as positive, and were given further examination or a pap smear.
This turned up 1,874 cases of precancerous lesions, 72 percent of whom received treatment.
Over six years, the group recorded a total of 167 cases of cervical cancer and 83 deaths from this disease.
The investigators recruited a "control" group of 31,000 women, who were not screened.
Comparing the two groups, women who had been screened were 25 percent less likely to develop cervical cancer and 35 percent less likely to die from it.
Combined with "good training and sustained quality assurance," the technique is an excellent preventative tool for developing countries, believes Sankaranarayanan.
The vinegar test was pioneered by doctors from Johns Hopkins University in Baltimore, Maryland, who assessed it for safety and effectiveness among 10,000 women in Zimbabwe in 1999. The new trial takes this process a major step further.
There were 493,000 new cases of cervical cancer and 273,000 deaths from the disease in 2002, according to IARC figures quoted in The Lancet paper.
Once the cancer, initiated by the human papilloma virus, spreads beyond the cervix, the chances of survival fall, which means it is vital to spot tumorous cells in the earliest possible stage.
But in poor countries, the pap smear, as well as the newly-introduced cervical cancer vaccine, are often too expensive or unavailable.