For the first time, scientists have proof that condoms offer women impressive protection against the virus that causes cervical cancer.

A three-year study of female college students — all virgins at the start — found that women whose partners always wore a condom during sex were 70 percent less likely to become infected with the human papilloma virus, or HPV, than those whose partners used protection less than 5 percent of the time.

"That's pretty awesome. There aren't too many times when you can have an intervention that would offer so much protection," said Dr. Patricia Kloser, an infectious-disease specialist at University of Medicine and Dentistry of New Jersey who was not part of the study.

Condoms have been shown convincingly to prevent pregnancy and AIDS. But conservatives who want to see abstinence taught in schools have long argued that condoms do not protect well against diseases such as HPV, because men can spread the virus to women from sores on their genitals outside the area covered by a condom.

However, the researchers at the University of Washington found that the chances of HPV being spread that way appear to be small.

Human papilloma virus — which can cause cervical cancer, genital warts and vaginal, vulvar, anal and penile cancers — is the most common sexually transmitted disease, infecting about 80 percent of young women within five years of becoming sexually active. An estimated 630 million people worldwide are infected.

The virus is spread during sex from contact with the sores, or lesions, that develop around infected cells.

Often, the virus is killed by the immune system, but in some people HPV can take hold and cause lesions that can turn cancerous years later. Cervical cancer strikes about 10,520 American women and kills about 3,500 each year. Worldwide, about 500,000 women develop cervical cancer and nearly 300,000 die from it every year.

In the HPV study, published in Thursday's New England Journal of Medicine, none of the women who reported that their partners always used condoms developed lesions during the three-year period. Fourteen women whose partners used condoms less regularly got lesions.

Twelve of the 42 women who said their partners always used condoms became infected. Rachel Winer, a researcher in the university's epidemiology department, said it could be that the couples did not use the condoms correctly or had some sexual contact before putting on a condom.

Recent medical advances might someday render the condom debate moot: Earlier this month, the government approved the first vaccine against HPV, and public health officials are urging that girls be routinely vaccinated before they become sexually active.

The study comes as the Food and Drug Administration is revising rules for the claims that manufacturers can make on how well condoms prevent sexually transmitted diseases.

Packages now must state: "If used properly, latex condoms will help to reduce the risk of transmission of HIV infection (AIDS) and many other sexually transmitted diseases." But revisions were ordered by Congress in 2000 amid pressure from conservative groups demanding "medically accurate" claims as to condoms' effectiveness.

Safe-sex advocates warn that changing the wording would undermine public confidence in, and use of, condoms.

At the time, there was solid evidence only on how well condoms prevent pregnancy, HIV and, in men, gonorrhea. Recent research has produced strong evidence condoms protect well against gonorrhea, chlamydia and herpes in both men and women, said Dr. Ward Cates Jr., president of the Institute for Family Health at Family Health International. This study adds HPV to that list, he said.

"This will help clinicians to counsel their patients about the effectiveness of condoms to reduce another of the sexually transmitted infections — if condoms are used consistently and correctly," Cates said.

The researchers invited 24,000 female students ages 18 to 22 at the Seattle university to be in the study. Starting in 2001, they followed 82 from before their first vaginal intercourse, testing the women for HPV with swabs of the cervix and other genital areas every four months. The women kept online diaries detailing each act of intercourse, including condom use and whether there was any genital contact without a condom.

Winer said previous HPV studies either showed no protection from condoms or were inconclusive. This one included only virgins and collected more details, and the computer diaries helped women be more honest about condom use than those in studies where people are interviewed about their sexual behavior, she said.

"This is about as ideal a study as you can get," said Dr. Tom Fitch, a San Antonio pediatrician and board chairman at the Medical Institute for Sexual Health, which stresses abstinence and monogamy as the only sure ways to prevent sexually transmitted infections.

Nevertheless, Fitch noted that some consistent condom users still were infected with HPV. Fitch and Kloser also suggested that the results in the real world — say, among poor, inner-city women — might be different from those with college women.

Fitch said several studies have shown that at most, 50 percent of people reported using a condom every time they had sex.