The elections will be Myanmar's first openly contested polls in 25 years, following decades of military rule.
The ruling Union Solidarity Development Party, which has been in power since 2011, is holding a rally in Yangon.
Aung San Suu Kyi's National League for Democracy (NLD) is expected to make major gains on Sunday, though she is barred from the presidency.
But the BBC's Jonah Fisher in Yangon says there are no reliable opinion polls in the country, also known as Burma, so no-one really knows how the vote is going to play out.