Participants included environmentalists, scientists, regional lawmakers, and representatives of the regional administration. Supporters of various political parties also took part.
The future pipeline is expected to run some 700 meters from Lake Baikal.
Irkutsk Oblast Governor Aleksandr Tishanin on March 13 said he was concerned about possible oil spills into the lake, which contains an estimated one-fifth of the world's fresh water. Tishanin said an oil spillage would have "irreversible" consequences.
The planned pipeline is designed to pump Russian oil to Asian countries. Its first section should be completed by 2008.