A lawsuit which accuses tobacco firms of duping smokers into thinking low tar or "light" cigarettes are less harmful has been given the go ahead in the US.
Experts say low tar cigarettes are just as bad for health
Federal judge Jack Weinstein has ruled that the case can proceed as a class action, involving potentially tens of millions of plaintiffs.
Experts estimate that if successful, the case could cost the tobacco industry up to $200bn (£105bn).
Defendants include Philip Morris, RJ Reynolds and British American Tobacco.
They are joined by Lorillard Tobacco and Liggett Group.
Low tar cigarettes were introduced in the 1970s.
Spokesmen for Reynolds American, parent company of RJ Reynolds, and UK company British American Tobacco said each would now be appealing the judge's decision.
The appeal is likely to last up to a year.
Altria, parent of Marlboro-maker Philip Morris, said the ruling could see it delay the spin off of its Kraft Foods unit.
Lawyers for the plaintiffs argue that the tobacco companies in question reaped between $120bn to $200bn in extra sales through the deception that light cigarettes are less harmful than full strength versions.
"They [the cigarette firms] understood that they were selling death," said attorney Michael Hausfeld.
The question, he added, was "how to disguise it...They put on 'lights'."
Defence attorneys had argued that the lawsuit relied on flawed data.
They also said that without surveying each and every smoker in the lawsuit it would be impossible to determine their motives for buying light cigarettes.
The link between smoking and lung cancer was first confirmed in 1954.
British American Tobacco said that to date there have been 60 class actions cases against tobacco companies in the US and none have been successful.