Official results show that 59.6% of the electorate approved the agreement, opening the door for all EU citizens to come and work freely in Switzerland.
Turnout was just under 51%, which is above average for national referenda in Switzerland. Urban regions and all of the French-speaking cantons voted in favour, but the Italian-speaking Ticino and three cantons in the majority German-speaking part voted against.
The poll had a greater EU relevance for the Swiss as, in the event of a 'no' vote, a "guillotine" clause would have suspended a number of related trade agreements between the Alpine country and the EU, which had been negotiated in 1999.
"This (vote) is a key agreement for relations between the European Union and Switzerland. The positive vote from the Swiss people opens the way to strengthening ties in areas of mutual interest," Commission President José Manuel Barroso said in a statement.
The Czech EU Presidency issued a statement congratulating the people of the Swiss Confederation for having expressed "the wish for continuity in the co-operation with the EU based on the freedom of movement of persons, one of the fundamental European freedoms, which applies to all member states of the European Union".
Bulgaria and Romania also expressed their satisfaction over the results, EurActiv Romania and Dnevnik, EurActiv's partner in Bulgaria, reported.
Jacques de Watteville, the Swiss ambassador to the EU, recently explained in an interview with EurActiv (04/02/09) that the Swiss have been well aware of the referendum and the stakes involved. All the major political parties in his country were in favour of extending workers' rights to Bulgarian and Romanian citizens, with the exception of a third of the UDC party of businessman and populist politician Christoph Blocher, he explained.
The 'no' campaign played on fears about waves of immigrants from Bulgaria and Romania, portrayed as black crows on huge posters across the country.
Right-wing politicians even used the Commission's conclusions in its latest monitoring reports on Bulgaria and Romania to convey the impression that the citizens of both countries will bring organised crime and corruption to Switzerland.
The next such report on Bulgaria and Romania, under the 'Cooperation and Verification Mechanism' introduced with their accession in January 2007, has wisely been delayed until 12 February, after the referendum, a Commission source told EurActiv.
