Voters appear to have accepted a proposal for a five-year ban on genetically modified organisms (GMOs) in Swiss agriculture.
The electorate have also voted on a separate proposal to ease restrictions on Sunday shopping, which is being challenged by trade unions.
First trends, compiled by the gfs Bern polling institute on behalf of the Swiss Broadcasting Corporation, show a narrow majority of voters endorsing a people's initiative for a temporary ban on GMOs.
No trends were available for the referendum on Sunday trading.
The vote on the GMO moratorium comes after parliament passed a new law in 2003, which allows GM crops in Switzerland under certain conditions.
At the height of the debate environmentalists and consumer groups started collecting the necessary signatures to put pressure on politicians and let the electorate have the final say.
Supporters of the moratorium argue GMOs are neither in the interest of consumers nor of Swiss farmers, and that GM-free agriculture is an opportunity for farmers to improve their marketing for natural production methods.
Consumers and research
The lobby groups, supported by the Greens and the centre-left Social Democrats, say the proposal is not targeting research, but would give more time to consider the potential risks of GMOs.
The government, the business community as well as the main centre-right and rightwing parties have all come out against a temporary ban on GMOs.
They say the current law contains enough safety guarantees and a ban could be detrimental to biotechnology research in the country.
Surveys in Switzerland and EU countries found that consumers have little interest in GM food.
The electorate overwhelmingly voted down a far-reaching ban on GMOs in 1998.
Unions and church
In a separate vote, the Swiss had their say on an amended labour law, which eases restrictions on Sunday trading at the country's main railway stations and airports.
The trade unions, supported by the centre-left Social Democrats and the country's main churches, mounted a challenge to the revised legislation. They are concerned that relaxed regulations will lead to a seven-day working week.
Both the Protestant and Catholic churches have sided with the unions, warning that Sunday risks losing its special status.
The government, three of the main centre-right and rightwing parties, as well as the business community have come out in favour of more relaxed rules.
They say shopping at the country's main public transport hubs meets a need among a growing number of consumers and is in line with the latest commercial trends.
Shops in Switzerland usually remain closed on Sundays and public holidays, but numerous exceptions have been introduced, mainly in tourists areas, and at service stations, airports and railway stations.
Under a 2003 law, the Swiss parliament approved the use of GM crops under strict conditions.
Surveys have shown that consumers have little interest in GM products.
Sunday work in Switzerland is banned in Switzerland in principle under 19th century labour legislation.
Shop opening hours are decided at a regional and local level and the authorities have eased Sunday trading restrictions over the past decades.