Sunday's referendum in southern Sudan gives voters a choice between staying united with the rest of Sudan or becoming an independent country.
The poll was agreed to in the 2005 Comprehensive Peace Agreement that ended Sudan's 21-year north-south civil war.
Voters entering polling booths will see two symbols. One shows two hands clasped together, symbolizing unity. The other shows the single palm of a hand, symbolizing separation.
Most analysts predict southerners will choose independence. The new country would be Africa's first since Eritrea won independence in 1993.