The tax rise is part of a wider anti-smoking campaign
The largest-ever single increase in US federal taxes on cigarettes has taken effect, almost tripling the tax on a packet to more than $1.
The Obama administration plans to use the money to pay for health care for uninsured children.
Health campaigners say raising taxes on cigarettes in the middle of a recession is a good way to get more people to stop smoking.
A 20-a-day smoker will have to pay an additional $225 (£156) a year.
Similar tax increases went into effect for cigars, pipe tobacco and chewing tobacco.
Help to quit
Paola Munoz is exactly the type of person they are hoping to reach, the BBC's Stuart Cohen reports from Washington.
She has been smoking for more than three years but her New Year's resolution this year was to quit.
She says she has already cut down from one pack a day and the new tax will help her give up the habit altogether.
"I buy a pack every three days," she says.
"With the tax it is going to be around $6 and some change. And I don't want to pay that
so I'd rather just quit, and this is a great excuse to go cold turkey and quit completely."
The cigarette companies have not been standing idly by.
They raised prices on cigarettes a few weeks ago to start making up for the money they expect to lose in sales.
The tax increase is just the first step in a newly energised anti-smoking campaign in the now Democrat-controlled Congress.
They are considering a law that would allow the Food and Drug Administration to regulate tobacco - something the industry has successfully fought for years.