Estelle Osowiecki sashayed up to the microphone on the stage near Baltimore's Inner Harbor Saturday night and announced that the Polka Stars, a Polish American dance troupe, would perform a dance called the hopak.

A hopak? The Ukrainians in the crowd at the Slavic American National Convention couldn't believe their ears. A HOPAK?! "The hopak is a Ukrainian dance! The Poles have their own dances," cried an incredulous member of the Lyman Ukrainian Ensemble, twisting and untwisting the embroidered cuff of his costume as he watched the stage.

No sooner had the music begun than small boys dangling from the stage scaffolding, Ukrainians all, began to hoot.

"Stick to your own dances!" one roared gleefully into the evening sky. "Yaaaghh, yaaghhhh! BOOOOOOOO." The less dumure members of the crowd, who happened to be in the majority, chimed in.

But the heckling didn't stop the Polka Stars, at least not right away. Miss Polonia of Greater New York does not quit kicking just because someone in the crowd is not fond of the sequined stars on her bloomers.

The music faltered, resumed, then faltered again. Someone was wrestled away from the phonograph wire. That did it.The Polish American Polka Stars marched off stage and made a beeline for the Ukrainians.

A loud argument ensued that ended peacefully when the Ukrainian dancers took the stage and put on a stunning performance.

The Slavic Americans, among the latest ethnic groups out of the melting pot, held the first Slavic American National Convention this weekend in Baltimore's new Convention Center. The organizers eventually hope to unify some of the estimated 20 million Slavic immigrants and refugees who have made the United States their home.

But if the idea of the conventions was unity, the reality, particularly the folk dance competition at the end of the day, was something else. Complicated doesn't begin to describe it. Neither does organized, and Byzantine only comes close. The tip-off was the atlas disguised as a banner hanging outside the hall:

WELCOME to the SLAVIC AMERICAN CONVENTION--

Boehimians, Moravians, Slovaks, Serbians, Crotians, Polish, Ruthenians, Ukrainians, Russians, Byelorussians, Solvenians, Bulgarians, Macedonians.

The Slavic Americans are nothing if not a diverse minority.

It didn't get any better once you got inside convention hall, where clusters of dancers in bright costumes scurried about biting their fingernails and tapping their feet.

"Do not call us Russians," said the Byelorussian dancer.

"Remember, we are not Ukrainians," rumbled the Capatho Ruthenian

"please," said the Ukrainian, stretching his legs. "We are not Polish."

"Don't forget," said the Pole, "we are not from the east of Poland, we are from the west ."

"Americans think anything Slavic is Russian," said Alla Olga Romano, a Byelorussian. "That is really unfortunate. The Russians have done to my people what the Germans did to the Jews."

Some of those gathered outside near the stage before the contest began spoke emotionally of the labor unrest in northern Poland. "The Russians wouldn't dare go into Poland," said Sister Milada, a Czech nun from the Ukrainian Catholic Church. "Not after Afghanistan. They don't need another Afghanistan in Poland."

But most were willing to leave politics to the delegates at convention hall -- where workshops were conducted on Slavic affairs, domestic politics, and human rights -- and the talk soon reverted to the polka.

"Where's the polka band at?" a man had demanded earlier of the woman at the information desk. "They're supposed to start at 8, and I can't find them."

"Downstairs," she said smiling sweetly and smoothing the folds of her dirndl skirt.

"I just came from downstairs," he said less sweetly. "They sent me back up here."

"Well," she replied, taking a deep breath for the same phrase she's been employing since 9 a.m., "come back here in about 20 minutes. The man who knows about that will be here by then."

That man never showed up. But there was another fellow beside the stage who'd made his presence known almost as soon as the Polka Stars started dancing.

"You ought to be ashamed of yourselves," the old man yelled through cupped hands. "Why don't you all go work in a cocktail bar?"

The Polka Stars hopped and stamped doggedly on, their sequined costumes flashing and winking in the spotlight.

Boom, crash. Four male dancers swung four young women overhead, then out into midair. The women, looking more like star-spangled cowgirls than Polish maidens, turned cartwheels and kicked up their skimpy skirts, in a manner not seen in old Krakow.

The polka is essentially six steps and a hop. 1,2,3-hop-4,5,6. That's it.

Amazingly complicated for a dance hall step that's been around for more than a hundred years.

The dance became popular in the 1830s, the step for everyone who wasn't anybody in Central and Eastern Europe. It eventually debuted in polite society, a trifle slowed, as the waltz, the dance that swept dizzy Vienna off its feet.

The Poles claim the polka as theirs, but derivations of it were popular throughout what once was known as Bohemia. When large numbers of Slavs emigrated to the United States in the late 1880s, they brought the dance with them.

"I come from Pottstown," Thomas P. Colihan is saying. Colihan is with the Sunshine Polka Dancers of Washington, who boast perhaps of the tiniest polka dancer, age 4, the crowd saw. "My mother's name was Wydrochowska. She emigrated from Poland in 1980. My father worked in the mines. He died when I was 5, and my mother was always pretty quiet, but I had an aunt who ran a saloon up there, and she had a jukebox stuffed with all the old tunes. The people up there still love to polka. You'll see them in the bars any Friday or Saturday night."

"The American polka is different," says a Czech emigre. "The music is slower, but the dancing, ah, more hectic."

By the time the Polka Stars had left stage, the crowd had grown to 1,500. The Polish American food vendors had long abandoned their steaming trays of sausage, pierogies, kielbasa, and stuffed cabbage and moved with everyone else toward the brightly lit wooden stage.

"They told me 100,000 people would be here today," sighed one man, loading his truck full of Polish hot dogs and eyeing the comparatively small crowd. "They said 100,000, I got hot dogs for 100,000." "Always the optmist, said his wife.