Final rallies were held on Saturday ahead of the Presidential and Parliamentary elections.
The ruling Chama Cha Mapinduzi (CCM) party is said to be ahead in opinion polls, but observers expect the result to be close.
Four opposition groups are backing one candidate, 62- year-old Edward Lowassa , a former CCM member.
Some of the major issues for the almost 23 million registered voters include access to clean water, improved health care and better education.
President Jakaya Kikwete, who is standing down after two terms, has called for peace ahead of the election.
Tanzania’s Works Minister, Mr John Magufuli, 55, is running on the ruling party’s platform.