Federal mining regulators say 2012 had the lowest injury and fatality rates on record.
The Mine Safety and Health Administration says the number of U.S. mines fell by about 120 last year, but the number of miners working was actually up by about 6,500.
In all, MSHA says 35 miners died on the job in 2012, tying the record low set in 2009.
Nineteen deaths occurred at coal mines, the second-lowest number ever.
Sixteen miners died in on-the-job accidents at metal and nonmetal mines. MSHA said that equals the record low set in 2011.
MSHA chief Joe Main said Monday the numbers show that regulators and operators are moving in the right direction.