California voters will decide in November whether to require special labels for foods that contain genetically modified ingredients.
Advocates collected more than half a million signatures to qualify the measure for the November ballot. It was certified Monday by the state.
The vote will be a test of consumer attitudes about the merits of genetically engineered crops.
Supporters say if it passes, it will be the first law in the country to require labeling of such a wide range of GMO foods. It would require most processed foods by 2014 to bear a label informing consumers that they contain ingredients derived from plants whose DNA was manipulated.
Meat and dairy foods would not need labeling even if the animals are fed with genetically engineered grains. Opponents have criticized that exemption.