Brown's agency has been running an investigation into the business practices of the companies and Thursday ordered the firms to turn over documents related to claim denials and rate hikes.
"We have been looking at these companies for a number of months and are very concerned that some of them are unjustly raising premiums and denying payment of legitimate claims," Brown said in a written statement.
The companies subpoenaed include Anthem Blue Cross, Aetna Health and Kaiser Permanente. Anthem has proposed a 39-percent increase in the premiums charged to many of its customers in California.
Brown said the subpoenas involved "pay-for-service" health plans in which doctors and hospitals, rather than an HMO, are directly reimbursed by the insurers.
Brown is a Democratic candidate in this year's race for governor.
Aaron Carter is still in love with Hilary Duff
NBC reportedly holds celebs hostage to Jimmy Fallon's show