Among communits states, Yugoslavia enjoys special favor in the United States. It put the word "Titoist," meaning nationalist, not run by Moscow, into the language, and it has followed a relatively open internal policy -- partly to accommodate its Western friends -- since Marshal Tito's famous break with Moscow in 1948. Why, then, have the Yugoslavs been running a nasty political trial the past three months, one that has troubled various Yugoslavs, including some in the leadership, and that has severely embarrassed Belgrade abroad?

The defendants are six modestly known intellectuals, members of the small familiar dissident fringe, clustered around Marshal Tito's old nemesis, Milovan Djilas, that the authorities have more or less tolerated since the early 1970s. For their casual and individual participation in the half-meetings, half-social events of Belgrade's "free university" community, the six were charged last fall with organizing a conspiracy to subvert the system. It is a measure of the charges that a leading piece of the evidence cited against one defendant was a copy of his English-language master's thesis, written while he was a graduate student at Brandeis University and then stowed in his desk drawer.

There is a tendency in the West to let the Yugoslavs off easy. After all, it is said, they are more liberal than other communists and other East Europeans; being multi-ethnic and multinational, they've got to be extra careful; they are still feeling the post-Tito jitters; they face wracking problems of economic deterioration and internal reform. To which, the United States government, which has said not one word about the trial, adds (under its breath), it is in the American interest to settle Yugoslavia down as a stable buffer against Soviet expansion on a strategic front.

Yugoslavia's assorted dilemmas cannot be denied. It is true, too, that the Yugoslav authorities have shown in recent days -- by discharging one defendant, severing the cases of two and reducing charges against the other three -- that they realize how weak the case is. The fact remains, however, that Yugoslavia has a system that exposes it to indefinite crisis. As long as a single communist party demands to monopolize all political power, the country invites alternating impulses of popular challenge and official repression. This goes on within a narrower band than in other Communist-ruled countries but it is significant and ugly all the same. Here is the meaning of the case of the Belgrade Six.