It's the 9th annual Winter Classic at Clark Park in southwest Detroit.
Detroit Police are trying to get a victory against Detroit Firefighters, who have dominated the series, winning all but one game.
The game doubles as a fundraiser for Clark Park youth hockey, targeting urban areas.
Detroit Firefighters arrived in style just minutes before the game in a clown fire truck.
They jumped out to an early lead 4-0 in the first period.
There's a lot of good natured trash talking, but both agencies say they are family on and off the ice.