Karl Marx's birthplace is a stately three-story house that has been a fixture of this ancient town on the Mosel River since it was built in 1727. What is changing are the large groups that visit almost every day from China, one of the few countries in the world still under the control of something calling itself a Communist Party.

Chinese tourists have started to become common in Europe as China has become richer and tourist agencies have sprung into action. Trier is a worthy destination by any standard, having impressive and important Roman ruins as well as an 11thcentury cathedral built in the very place where Emperor Constantine's mother first built a church in the fourth century.

But the Chinese clearly come to see the place where Marx was born in 1818, and the local authorities try to take full advantage of it, promoting their city in China itself and with the travel agencies that serve Chinese tourists.

They even offer cultural sensitivity training for merchants, restaurateurs and others in Trier, instructing them in the finer points of dealing with Chinese customers. The number 250, for example, which is a kind of slang for ''stupid'' in Chinese, is to be avoided, and so is wrapping paper in white, the color of funereal robes, or yellow, by custom reserved for the emperor. It is also important to hand over visiting cards rather formally, with two hands, not just one.

''Years ago, state visitors from China used to come to see the Marx House,'' said Robert Noll, chief of the Trier Tourist Development office. ''They would spend a couple of hours, take a picture and then leave. But in the late 1990's, when Chinese tourism picked up in Europe, we saw the opportunity.''

''Now the Chinese are second after the Dutch in overnight stays,'' Mr. Noll continued, adding that about 100,000 Chinese citizens visited Trier last year, and about 40,000 of them spent at least one night.

''And they come all year,'' he said, ''even in the low season.''

But what of the Chinese themselves? After all, the ruling party in China might call itself Communist, but China is capitalist today, having rejected Marxism in practice if not in theory. Do they come to Trier as pilgrims to a kind of shrine, though one widely seen as a historical relic in the West?

''Nah,'' one man, who said he was from Harbin in the far north of Manchuria, said dismissively. A minute earlier, the man had struck a sort of mock revolutionary pose for a photograph next to the inscription identifying the house as Marx's birthplace. He did not seem reverential.

''It's just a stop on the tour,'' he said. ''We went to Paris and Brussels, too. It's a six-day trip.''

But a woman who seemed to have a bit of the schoolmarm in her took the pilgrimage more seriously, arguing that China had a need for Marxism.

''If Europe had been the same in Marx's time as it is now, there would have been no Marxism,'' she said. ''But there was a big difference in Marx's day between the rich and the poor. And if China in the past was like China is now, we wouldn't have had any need for Marxism either.''

''But China was very, very poor,'' said the woman, who did not give her name. ''And if we hadn't had Marxism, we wouldn't be the way we are today.''

Judging from the comments in the Marx House guest book, most of the Chinese visitors seem to agree, extolling him as a great figure whose name will burn brightly in China forever.

But widely spaced on the book's pages were some dissenting opinions, all unsigned, one going so far as to bemoan what the writer described as the Communist authorities' use of Marxism as a pretext for oppression.

''Marxism is not bad,'' one person wrote. ''But it is a dream, beautiful only as philosophy.''

The Karl Marx House is a project of the Friedrich Ebert Foundation, which is run by Germany's left-of-center Social Democratic Party. The foundation bought the house in the 1920's; it was taken over by the Nazis before World War II. After the war it was returned to the Social Democrats, who turned it into a museum.

An extensively renovated permanent exhibition opened a few months ago, and it contains items that party-line Chinese have found objectionable. One of the opening rooms consists of a screen on which various sayings by Marx and about him are projected in German, French, English and Chinese.

These include such Marxian classics as: ''Religion is the sigh of the oppressed; it is the opiate of the masses.'' But there is also a famous line from Germany in 1989 when the Berlin Wall fell. It is: ''Marx ist Murx'' -- Marx is trash.

And on an upper floor there is a short portion of the exhibition devoted to Chinese Marxism, referring to the Long March led by Mao in the 1930's as a ''mythologized'' event and speaking of the massacre of thousands of students and others during the violent suppression of the Tiananmen democracy movement in China in 1989.

''Some visitors have said to me, 'Why do you show old things when the new China is so beautiful,' '' said Beatrix Bouvier, the museum director, who oversaw the recent renovation of the exhibit. ''I tell them, 'We are a museum so our duty is to deal with history, and especially we Germans know that we shouldn't forget history.'

''Official Chinese history is not a history that I agree with. And I cannot accept that a Chinese tells me what I have to show in a German museum.''

Photos: A Chinese tourist posed at Karl Marx's birthplace, a house in Trier. As China departs sufficiently from the economic constraints of Marxism to enable many of its people to visit Europe, the house has become a major attraction.; A sign at the Karl Marx House reflects the increasing number of Chinese visitors, giving the direction to the restrooms in their language. (Photographs by Martin Specht for The New York Times)

Map of Germany highlighting Trier.