The FBI performed nearly 2.8 million background checks on people wanting to buy guns in December, a record month that capped a record year.
The numbers from the FBI's National Instant Criminal Background Check System on Wednesday did not show how many firearms buyers actually took home from federally licensed gun stores. Some purchasers may have bought more than one weapon.
Data is made publicly available, but the FBI but does not generally try to explain increases in the number of checks.
However, recent figures have shown more checks are performed after gun-related tragedies such as the December 14 school shooting in Newtown, Connecticut, that killed 20 children and 6 adults.
Data also showed the FBI generally is asked to run more checks in November and December, the holiday shopping months.
The FBI performed more than 2.78 million checks in the final month of the year. That followed a record November. For 2012, the agency ran more than 19.5 million background checks, another record that represented a year-over-year increase of more than three million.
Under federal law, sales staff at stores licensed by the government to sell firearms are required to call the FBI or another approved agency to make sure the buyer does not have a criminal record or a history of serious mental illness, which would legally prohibit the sale.
The system does not account for all U.S. gun purchases, however. Many gun shows are not covered and private sales, such as one hunter selling a weapon to another, also are not subject to checks.