The huge crowds trying to enter the museum - queueing in the cold for up to four hours, were making their working life intolerable - the staff say. They want a special bonus and extra time off.
The result has been a pounds 500,000 loss for the museum; thousands of bemused tourists and angry French art-lovers; and the likelihood of even bigger queues when the museum and exhibition finally reopen.
The strike is one of a series of industrial actions in recent weeks that have crippled high-profile French institutions. Other icons of modern and traditional France infected by what used to be called the "English disease" include the Eiffel Tower, the huge, new national library and the Palace of Versailles.
There have also been strikes at the main European Viagra manufacturing plant by the Loire; by train drivers in Marseilles and Bordeaux; by schools inspectors; and by Air France flight attendants.
On Wednesday, there was even a demonstration in Paris by the police, protesting against plans to shut quiet, rural stations and transfer officers to troubled suburbs of big cities.
The wave of unrest has no single cause. It is all the more surprising because the French economy continues to perform well and Lionel Jospin's government remains popular. If there is one common denominator, it is the gradual attempt to introduce more flexible working practices and labour contracts into France.
The clutch of strikes at cultural institutions is also blamed by the unions on the Culture Minister, Catherine Trautmann, who, they say, is inflexible and unwilling to use her own authority to solve disputes.
The strike at the Musee d'Orsay is especially embarrassing for the French government. The museum, in a former railway station on the left bank of the Seine, opposite the Louvre, has become one of the most visited cultural sites in Paris since its opening in December 1986. It contains most of the national collection of Impressionist paintings, as well as a series of high-profile, temporary exhibitions.
Members of staff complain that the entrances to the museum were badly designed, and that the exhibition spaces are too poky, causing huge queues whenever there is a popular show. The Millet - Van Gogh exhibition, which began on 17 September and closes in January, has been a huge success, with almost 200,000 visitors in October. The exhibition is the first attempt to trace the debt of Vincent van Gogh to the French 19th-century landscape painter Jean-Francois Millet, on whose paintings some of Van Gogh's best- loved canvases were based.
A radical redesign of the museum's entrances is promised for next year. Meanwhile, one museum worker said: "People are waiting two or three hours in the cold. Some of them get very aggressive. Too many tickets are being sold for the space there is".
The unions claim that the staff should be rewarded for their stress and extra work. The management has offered a pounds 70 bonus and two extra days off. The unions want pounds 160, three days off and payment for half the days they have been on strike.
n France adopted a Bill yesterday that gives the country one of the world's toughest laws on the use of performance-enhancing drugs by athletes, responding to the furore during the Tour de France, when there were revelations of widespread drug use by riders in the international cycling race.Reuse content