Condoms are ineffective in the fight against AIDS. Abortion increases the risk of breast cancer. An emergency contraceptive, recommended as safe and effective by two independent scientific advisory panels, is not approved for over- the-counter status in the United States.

These are just a few of the positions the current US administration has taken, in each case ignoring scientific evidence to the contrary. It arrived at these conclusions by either disbanding scientific advisory committees or packing them with candidates selected for political, rather than scientific, reasons. It has restricted federal scientists' ability to talk freely with the media and with their colleagues. Most recently, it announced that the US Department of Health and Human Services (HHS) would determine which federal researchers can participate in scientific panels of the World Health Organization (WHO).

When a country as powerful as the United States makes decisions, however, the effects are felt far beyond its borders. That was evident at the XV International AIDS Conference, held in July in Bangkok. The conference attracted nearly 20,000 delegates from 160 countries, but a new HHS policy restricted the number of US federal scientists to fewer than 50 (Nat. Med. 10, 657; 2004). Because the policy was announced after many researchers had made plans to attend the conference, dozens of sessions—including sessions where US scientists were supposed to train researchers from developing countries in grant writing and designing clinical trials—were canceled.

The biannual AIDS conference is one of only a few meetings of its scale that allow scientists and others who work with patients in poorer countries access to such expertise. The HHS has cited travel costs to Bangkok as the reason for the small contingent. But the agency did not respond to offers of financial assistance from conference organizers and denied permission to attend the conference to a federal researcher whose trip would have been paid for by a highly visible journal.

Even apart from the conference, the HIV/AIDS field represents perhaps the most egregious of the Bush administration's scientific missteps. In January 2003, President Bush pledged $15 billion over five years for the fight against HIV/AIDS. The plan heavily promotes the 'ABC' approach of abstinence, monogamy and condoms—for some high-risk groups—to prevent HIV transmission, and earmarks a third of the funds for abstinence-only programs.

In practice, however, the use of condoms has been marginalized or dismissed altogether. For instance, guidelines published on 16 June by the US Centers for Disease Control and Prevention require organizations that promote HIV prevention and receive federal funds—even if the funds are not used for those prevention programs—to include information on the “lack of effectiveness of condom use.” As many experts at the conference noted, women and girls in the developing world often do not have the choice to abstain, and condoms offer them the best available protection.

Bush's AIDS plan also prohibits use of the funds to buy generic versions of antiretroviral drugs. Officials have said that the policy is in place because the US Food and Drug Administration has not approved the generic drugs as safe and effective. However, these drugs have been ratified by the WHO, which uses standards endorsed by many international bodies including the Global Fund to Fight AIDS, Tuberculosis and Malaria, the World Bank and Médecins Sans Frontières.

To make decisions that pander to conservative constituents when millions of lives are at stake is unconscionable. Last year alone, 3 million people died of AIDS-related causes and 5 million people became infected with HIV, more than in any previous year, according to a report by the Joint United Nations Programme on HIV/AIDS. The number of infections is surging in Asia, Eastern Europe and even in the United States.

At the Bangkok meeting, activists expressed their anger by dogging US officials at nearly every session, booing them at mentions of abstinence, carrying posters that declared “Science, not politics” and chanting “No more lies.”

But such histrionics are better left to activists. What can scientists do to change the administration's attitude to science?

On 8 July, more than 4,000 scientists, including 48 Nobel Prize winners and 127 members of the US National Academy of Sciences, sent a statement to the Bush administration, accusing it of manipulating and suppressing science to further its political agenda. The same statement had also been sent to the administration in February by 62 prominent scientists. On both occasions, officials dismissed the letter as wrong and misleading.

Previous administrations have generally been more responsive to the concerns of activists and scientists. But only conservative groups have the attention of those now in command. Writing letters that garner media coverage is a good start to bringing the problems out into the open. But it is not enough.

Scientists must band together and voice their dissent. Those outside federal agencies must align with those within and support them in resisting the administration's policies. Most of all, scientists must not let the administration silence their protests. What they must do—and continue doing until they are heard—is loudly and clearly counter the misguided policies with evidence-based arguments. Without resorting to chanting or posters, scientists must still find their way to demand, “Science, not politics.”