Bolivian President Evo Morales is taking his campaign to build a highway through pristine Amazon jungle directly to the affected communities, some of which have strongly protested the plan.
Officials and international observers came to Sunday's meeting in the jungle town of Oromomo, one of 69 communities in the TIPNIS reserve that are to decide by Aug. 20 whether they want the 200-mile (310-kilometer) highway, which is funded by Brazil. Each community gets one vote.
Morales government says the project will help the nation's economy. But Bolivia's main lowlands Indian federation has bitterly denounced it, saying it will cause environmental damage in a now-undeveloped area believed to hold deposits of minerals and oil.
The federation has urged a boycott of the consultation, arguing it is stacked in favor of Morales' side because it allows voting by recently arrived ranchers, coca farmers and other settlers whose connection to the land is less intense.
The controversy has caused a vexing problem for Bolivia's first indigenous president, setting him against some of the ethnic groups and environmentalists who had been among his strongest backers.
The consultation is the result of a new constitution that Morales helped to pass three years ago, which calls for Bolivia's indigenous peoples be consulted in matters affecting their lives and traditional lands.