A survey by the Federal Trade Commission (FTC) estimates that 27.3 million Americans have had their identities stolen in the last five years, including 9.9 million people in the last 12 months alone.
"These numbers are the real thing," says Howard Beales, the FTC's consumer protection chief.
As identities get stolen mostly for the purpose of creating bogus credit card accounts, financial losses are mounting.
Businesses have lost 48 billion dollars last year, with consumers losing five billion dollars.
"For several years we have been seeing anecdotal evidence that identity theft is a significant problem that is on the rise. Now we know.
"It is affecting millions of consumers and costing billions of dollars. This information can serve to galvanise federal state, and local law enforcers, the business community and consumers to work together to combat this menace," Beales said.
27.3 million Americans have been victims of identity thefts in the last five years, including 9.9 million people in the last year alone
The FTC, an independent consumer protection agency, said its survey found in the past one year that 3.23 million consumers discovered that new, unauthorised accounts had been opened in their names.
Identities also get stolen to enable the thief to rent an apartment or home, or to obtain medical care or employment, the survey revealed.
The FTC said that while most cases of identity thefts were linked to financial crimes, 15% reported that their personal information was misused in non-financial ways.
Identity theft helped criminals obtain government documents or tax forms, or by giving a false identity when questioned by police or caught committing a crime.
About one in four victims said they believed they were victimised as a result of lost or stolen credit cards, cheque books or other possessions.
Another 4% said they believed identity thieves got their information from stolen mail.