The American Cancer Society has cut off all funding to researchers who take money from tobacco companies after a university study funded by the tobacco industry allegedly understated the harmful effects of passive smoking.
The decision will take effect next year, affecting millions of dollars in grant money. The society funds 774 separate research projects worth some $350 million (£192 million).
Greg Donaldson, the society's national spokesman, said: "At any given time, the demand for our limited research dollars always outstrips the supply."
Mr Donaldson said tobacco companies "have a history of using their resources and influence to co-opt and cloud legitimate scientific discovery".
The society cites the example of a University of California at Los Angeles study that downplays the dangers of passive smoking, in which the society says its own statistics were misrepresented.
The incident partially triggered the new policy, which specifically cites tobacco industry attempts "to confuse public debate, to delay effective tobacco control measures and to buy the appearance of scientific legitimacy rather than to advance scientific knowledge".
The policy bans scientific investigators or health professionals who are funded by the tobacco industry for any project from receiving society research grants after July 1 next year.
The society already refuses to accept money from tobacco companies or their affiliates, or to collaborate with the tobacco industry at the community level.
The public response had been "overwhelmingly positive", Mr Donaldson said.
"We believe the elegance of our policy is that it respects and does nothing to penalise the academic and research institutions. We believe our policy, unlike some others, actually preserves and protects academic freedom and academic choice."
Academics have not publicly criticised the new guidelines as it would put them in the uncomfortable position of opposing an organisation dedicated to eradicating cancer.
American universities also say they have policies in place to prevent research sponsors such as tobacco companies from limiting their work or the release of their results.
The American Heart Association has indicated that it may consider a similar policy.
* A new study says that while fewer Americans are smoking, more university students are taking up the habit.
About one in three students smokes, up from one in five ten years ago. The study notes that tobacco companies have made university students their primary marketing target, giving away free cigarette samples at bars and sponsoring events in fraternities and sororities.