The measure passed 56 percent to 44 percent, with 100 percent of precincts reporting.
The Safer Sex in the Adult Film Industry Act requires adult film producers to apply for a permit from the county Department of Public Health to shoot sex scenes. The fee will fund periodic inspections of film sets.
Supporters, like the AIDS Healthcare Foundation, have been out in the streets giving away condoms to draw attention to the measure, which they said ensures workplace safety.
Opponents said actors are already protected. They said the industry regulates itself, works with Cal/OSHA on workplace safety and has a strict testing system.
Steven Hirsch, the co-CEO of L.A.-based Vivid Entertainment, a leading producer of adult films, said he hopes the county's Health Department won't start enforcing the new law until the legal arguments are played out in court. Hirsch claims nearby counties are already courting the adult film industry, which would cost L.A. County millions in lost tax revenue. Hirsh also said he was open to moving his business to another county.