European Union monitors said there have been no signs of trouble in the election, which will choose a new president, new members of parliament and local councilors, the BBC reported Thursday.
Incumbent President Levy Mwanawasa held a lead over main challenger Michael Sata in the most recent opinion polls, but support for the two candidates has fluctuated wildly during the campaign, the BBC said.
Mwanawasa, who is seeking a second five-year term, has focused on stability in his campaign. The Movement for Multi-party Democracy leader has pointed to the country's steady economic growth and reduction in foreign debt.
Opposition leaders have cited high unemployment and concern over health and education in their campaigns.
"We need to bring hope to Zambia. ... Can people eat inflation?" Sata said as he voted in Lusaka, the nation's capital.
Hakainde Hichilema, Godfrey Miyanda and Kenny Ngondo are also running for president.