Bahrainis, including the Shiite-led opposition, vote on Saturday to elect their second post-reforms parliament, amid allegations of a plot to keep Shiites under-represented.
Polls were due to open at 8:00 am, 24 hours after the close of campaigning.
Some 295,000 voters will be entitled to elect 39 MPs in an equivalent number of constituencies. There are a total of 207 candidates, including 17 women.
One seat in the 40-strong chamber has already gone to Latifa al-Qouhoud -- a woman who stood unopposed in her constituency -- making her the first female MP in the kingdom's history.
The Shiite majority, which has faced continuous discrimination in a country ruled by a Sunni dynasty, is out in force to achieve recognition.
But the main Shiite faction has had to ally itself with Sunni liberals and leftists. Like the Shiites, they boycotted the last legislative elections, in 2002, over discontent with reforms introduced by King Hamad.
The Islamic National Accord Association (INAA), which is the major Shiite formation in the kingdom, is fielding 17 candidates, while the leftist National Democratic Action Association has presented six candidates.
Both boycotted the 2002 polls protesting at the split of legislative powers between the parliament and an equally numbered upper chamber appointed by the monarch.
The outgoing chamber -- the first to be elected since parliament was scrapped in 1975 -- came about following major reforms that included turning Bahrain into a constitutional monarchy.