REFERENDUM: If voters approve the measure, Venezuela's constitution will be amended to remove all term limits for elected officials. That would allow President Hugo Chavez to run for re-election in 2012.
POLLS: Polls open at 6 a.m. (1030 GMT) and close when everyone who is in line at 6 p.m. (2230 GMT) has voted.
VOTING: Venezuela has 16.5 million registered voters, who will use touch-screen voting machines at 34,632 polling places.
RESULTS: First official results are expected about 11 p.m. (0330 GMT Monday).