ASHINGTON, Dec. 26 — The National Cancer Institute, which used to say on its Web site that the best studies showed "no association between abortion and breast cancer," now says the evidence is inconclusive.

A Web page of the Centers for Disease Control and Prevention used to say studies showed that education about condom use did not lead to earlier or increased sexual activity. That statement, which contradicts the view of "abstinence only" advocates, is omitted from a revised version of the page.

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Critics say those changes, far below the political radar screen, illustrate how the Bush administration can satisfy conservative constituents with relatively little exposure to the kind of attack that a legislative proposal or a White House statement would invite.

Bill Pierce, spokesman for the Department of Health and Human Services, scoffed at the idea that there was anything political about the changes, saying that they reflected only scientific judgments and that department headquarters had had nothing to do with them. "We simply looked at them, and they put them up," he said of the agencies involved.

The new statements were posted in the last month, after news reports that the government had removed their predecessors from the Web. Those reports quoted administration officials as saying the earlier material had been removed so that it could be rewritten with newer scientific information. The latest statements are the revisions.

Those statements have drawn some criticism, as did the removal, though like the issue itself it has gone largely unnoticed. Fourteen House Democrats, including Henry A. Waxman of California, senior minority member of the House Government Reform Committee, have written to Tommy G. Thompson, secretary of health and human services, charging that the new versions "distort and suppress scientific information for ideological purposes."

Gloria Feldt, president of the Planned Parenthood Federation of America, said the new statement on abortion and breast cancer "simply doesn't track the best available science."

"Scientific and medical misinformation jeopardizes peoples' lives," Ms. Feldt said, adding that any suggestion of a connection between abortion and cancer was "bogus."

The earlier statement, which the National Cancer Institute removed from the Web in June after anti-abortion congressmen objected to it, noted that many studies had reached varying conclusions about a relation between abortion and breast cancer, but said "recent large studies" showed no connection. In particular, it approvingly cited a study of 1.5 million Danish women that was published in The New England Journal of Medicine in 1997. That study, the cancer institute said, found that "induced abortions have no overall effect on the risk of breast cancer."

The Danish research, praised by the American Cancer Society as "the largest, and probably the most reliable, study of this topic," is not mentioned in the government's recent posting, which says the cancer institute will hold a conference next year to plan further research.

Dorie Hightower, a press officer at the cancer institute, attributed the revision to the institute's periodic review of fact sheets "for accuracy and scientific relevance." Asked whether the institute now thought that the Danish study failed on either count, Ms. Hightower said no. But she said there was no scientist available to explain the change.

As for the disease control centers' fact sheet on condoms, the old version focused on the advantages of using them, while the new version puts more emphasis on the risk that such use may not prevent sexually transmitted diseases, and on the advantages of abstinence.

Posted on Dec. 2, the new version begins, in boldface: "The surest way to avoid transmission of sexually transmitted diseases is to abstain from sexual intercourse, or to be in a long-term mutually monogamous relationship with a partner who has been tested and you know is uninfected. For persons whose sexual behaviors place them at risk for S.T.D.'s, correct and consistent use of the male latex condom can reduce the risk of S.T.D. transmission. However, no protective method is 100 percent effective, and condom use cannot guarantee absolute protection against any S.T.D."