Tulsa, Okla. - It's a big number, and it's going UP.
The Oklahoma Department of Public Safety has been studying the number of attacks on police officers nationwide and found that nearly 55,000 police officers were assaulted in 2011, the most recent year for which they have data.
DPS says about 25-percent of those suffered some kind of injury from the assault.
They also say the numbers have gone up steadily since 2009.
72 police officers were killed while on duty in 2011, many during traffic stops, some during domestic disturbance calls, and some were ambushed.