The Department of Public Health officials said at a news conference on Wednesday that they have started to hand out the grades.
Health officials have been inspecting food trucks, stands and carts for years but this is the first time the vendors will receive letter grades. The new rules require food truck operators to explain to customers why their trucks received less than an "A."
There are an estimated 6,000 food trucks and other smaller food vendors in Los Angeles County.
Health officials said it will take until June 2012 before all of them get a grade.