The Swiss people are going to the polls in a historic referendum which is likely to see Switzerland take a major step towards greater integration with the European Union.
Latest opinion polls indicate a clear majority in favour of the seven bilateral accords which make up the treaty with the EU. Most pundits have forecast around a 60 per cent vote in favour of the accords.
Advance and postal voting have already been taking place for some time. The polls will close at midday local time, and exit polls and first results from the smaller cantons - mainly in central Switzerland - are expected shortly afterwards. More than 4,600,000 people were eligible to vote.
The accords, signed in 1999 after five years of painstaking negotiations, have already been approved by the Swiss parliament. They were last month ratified by the European Parliament in a clear signal to the Swiss people and the 15 EU member states whose parliaments also have to approve the agreement.
The seven accords, designed to increase Swiss access to EU markets and open up Swiss markets, cover transport, trade, aviation, research, agriculture, free movement of people and public procurement. All seven have to be approved or else the treaty will be rejected.
Two small right-wing parties, the Lega dei Ticinesi and the Swiss Democrats, as well as about 10 groups, collected the 50,000 signatures needed to force a referendum on the issue. Opponents of the accords fear they will compromise Swiss independence and neutrality, and claim they are a stepping stone towards full EU membership.
The government, all four government parties, parliament and big business threw their support behind the accords, saying they are vital to Switzerland's economic and political future.
The main right-wing party in government, the Swiss People's Party, was divided over the issue, but its executive gave the bilateral accords a qualified "yes". This set it apart from a number of its branch parties, particularly in German-speaking central and eastern Switzerland, which voted to recommend rejection of the accords.
It was the People's Party, and its charismatic populist leader, Christoph Blocher, who led the successful campaign against membership of the European Economic Area, which the Swiss people rejected - contrary to government wishes -in a popular vote on December 6, 1992.
The latest campaign was lacklustre, but government ministers mounted an early and spirited campaign around the country in an attempt to avoid a repetition of the humiliation it faced in 1992.
Many observers are watching both the anticipated margin of victory and the turn-out figure in Sunday's vote. Although the government has made it clear a vote in favour of the bilateral accords is not a formal step towards European Union membership, opponents fear otherwise - particularly since the government's stated aim is full membership in the long-term.
Analysts say that, if the accords are approved, full EU membership is unlikely to occur before seven to ten years. Any attempt to enter the EU is likely to galvanize right-wing opposition, centred around Blocher and his party.
Nonetheless, a senior Swiss official told swissinfo last week that the campaign for full EU membership would begin on Monday - one day after the vote.
The accords themselves are scheduled to take effect from next January, provided they are also approved in the parliaments of all 15 EU member states.
swissinfo with agencies