American cigarette companies have been honest in highlighting the serious risks of smoking, a lawyer for the tobacco industry has told a US court.
Tobacco firms say they will disprove the claims
In a government lawsuit, tobacco firms are accused of lying about the effects of smoking over a 50-year period.
But a lawyer for Philip Morris said: "It's an unambiguous and clear message that we sell a dangerous product."
The $280bn (£156bn) lawsuit - filed by the Clinton administration in 1999 - is expected to last six months.
Presenting the industry's opening statements, lawyer Ted Wells said the conduct of some tobacco industry officials over the years may have been "regrettable".
But he said changes in how tobacco companies now market their products would help dismiss claims that they misled the public.
Prosecutors want the cigarette firms to surrender $280bn in profits accumulated over the past 50 years and impose tougher rules on marketing their products.
In its lawsuit, the government claims tobacco firms manipulated nicotine levels to increase addiction, targeted teenagers with multi-billion dollar advertising campaigns, lied about the dangers of smoking and ignored research about its impact on health.
A 1953 meeting in New York attended by executives from the country's top five cigarette makers resulted in a "massive 50-year scheme to defraud the public", the lawsuit claims.
The defendants include Philip Morris US, Reynolds American Inc, Lorillard Tobacco, the Leggett Group and Brown and Williamson, a US subsidiary of British American Tobacco.
The firms, which deny any wrongdoing, have been indicted under legislation drawn up to counteract Mafia infiltration of business.