Voters are heading to the polls to elect the first police and crime commissioners for England and Wales.
The elections are taking place in 41 police force areas - except in London - from 07:00 GMT until 22:00 on Thursday.
The new PCCs, which are set to replace police authorities, will set spending plans and have the power to "hire and fire" chief constables.
The results are expected to be announced on Friday, with elected PCCs assuming office from 22 November.
The government set up the commissioner role in what it describes as an effort to make police more accountable, with a single "figurehead" monitoring and ensuring performance.
As well as recruiting - or sacking - chief constables, commissioners will set out local policing priorities, report annually on progress and set out their force's budget and community safety grants.
Ministers say that the cost of commissioners and police and crime panels will be no greater than the cost of running existing police authorities. Commissioners are likely to be paid between £65,000 and £100,000 per year depending on the police force area.
Opponents say the move is a waste of money at a time when budgets are being cut and staff laid off.
The move to elect PCCs has been described as the biggest shake-up of policing for almost 50 years.
Labour and the Conservatives are fielding candidates in all 41 force areas.
The Liberal Democrats are not centrally supporting candidates but have not barred their members from standing. Lib Dems and members of the UK Independence Party are standing in just over half of seats.
Elections are taking place in all parts of England and Wales except London, where Mayor Boris Johnson and the home secretary both have oversight of the Metropolitan Police.
As well as elections for PCCs, voters in Cardiff South and Penarth, Corby and Manchester Central are also voting in parliamentary by-elections.
