28 doctors and nurses are facing charges in the crackdown on Shiite-led protests calling for greater rights. Monday's criminal court trial comes just four days before Bahrain's Sunni rulers seek to open talks with opposition groups in the Gulf island kingdom.
But Shiite leaders say authorities must end the protest-linked trials and release detainees before serious dialogue can begin.
The medical personnel are accused of joining the protests that began in February and spreading false information, seen as a reference to speaking to foreign media.
A separate trial began earlier this month for 20 doctors and nurses accused of alleged anti-state plots.
Bahrain's king is a key U.S. ally, and the nation is home to the U.S. Navy's 5th Fleet.