Trade barriers to Scotch whisky imports have been removed in South Korea - a nation that already ranks among distillers' most successful markets.
The new free trade agreement was struck between the European Union and the Seoul government.
The 20% spirits import duty is being phased out and complex requirements for labelling and warehousing removed.
The South Korean government also agreed to protect Scotch whisky and other European products against imitators.
During 2010 Scotch whisky was the UK's biggest export to South Korea, with top brands including Windsor, Imperial Classic and Scotch Blue.
Macallan and Glenfiddich are the most popular single malt brands.
It was the sixth biggest export market by value and the ninth biggest by volume, with direct shipments from the UK worth £153m last year.
The Scotch Whisky Association, representing distillers, said the free trade agreement with Seoul was "the most ambitious trade deal negotiated by the EU and the first with an Asian country".
It said Scotch whisky was expected to be one of the biggest beneficiaries.
The EU Trade Commissioner Karel de Gucht welcomed the potential for the Scotch whisky industry, saying an impact assessment points to a doubling of exports.
"This will make the product 20% less expensive, and it will make it much more competitive with the local brands, which represent the larger part of the market," he said.