The board of the state-chartered Colorado workers’ compensation insurance company accepted Ross’s resignation.
No reason was given for Ross’s departure.
Ross took over the position eight years ago. While he was president, Pinnacol lowered rates more than 50 percent between 2006 and 2010.
Last year, efforts to take Pinnacol private ruffled feathers among business leaders.
Pinnacol Board Vice Chairman John Plotkin will lead the company until a new CEO can be found. The search for Ross’s replacement will begin immediately.