The mayor of this ancient city was in an ebullient mood today. Appearing at a triumphant news conference, Francesco Rutelli dismissively waved two Italian newspapers and one from elsewhere in Europe that had warned of possible New Year's doom because of the Y2K computer bug and other problems, and proudly declared that "there were no catastrophes."

His pride was shared by many Italians who expressed undisguised glee that the country had defied both foreign and domestic skeptics who warned that Italy's late start in fending off potential ill effects from Y2K problems would turn it into the black sheep of Europe at the stroke of midnight on Dec. 31.

Instead of being laid low by electrical blackouts, food shortages and hospital shutdowns, however, Rome was struck by a bout of normality, as was the rest of the world. "There was complete tranquillity and security in the city," said Rutelli, overlooking the fact that nearly a million revelers were enthusiastically swigging spumante and throwing fireworks around Rome's streets in celebration of the new year.

As the first full business day of 2000 passed without incident today, many conspiracy-minded Italians said they were convinced that needless worry was provoked by computer consultants who sought to reap a financial windfall from the computer bug and foreigners who doubted Italy's digital skills. "The Bug Was a Dud; the Great Fear is Over," read a headline Sunday in La Repubblica, one of Italy's largest daily newspapers. "But Some Accuse: It Was a Bluff To Make Money."

Actually, "we were very nervous at midnight," said Toni Muzi Falconi, a technical adviser to the mayor on computer issues--and not only because foreign experts, ranging from the CIA to the British government, had sounded warning bells about Italian preparedness. "Maybe we were too cautious ourselves, or everybody was covering themselves" because of uncertainty about how bad the digital chaos might get. He said no one broke out champagne in the government's crisis center on New Year's Eve until more than 30 minutes after midnight.

The mayor and his aides attributed the absence of difficulties to a burst of hard work, most of it in recent months, by experts who rewrote software codes so that computers would recognize the year 2000. "Rome has never confronted an organizational challenge so complex," Rutelli told reporters.

The city spent millions of dollars to fix its own computer systems and took some extraordinary precautions. It instructed its computers, for example, that city employee paychecks for January are really extra pay for December, effectively freezing time in the second millennium to give itself some leeway to handle the unexpected.

As part of the nationwide effort to overcome the computer flaw--which as recently as a few weeks ago nearly half the Italian population said it had never heard of--the heads of large corporations formed joint task forces to share repair tips and contingency plans, said Augusto Leggio, technical director of the country's Y2K commission.

ENI, the oil and gasoline giant, spent tens of millions of dollars and "experienced nothing" over the weekend, said Michelle Favorite, a company spokeswoman. "I hate to sound so uneventful, but that's the story," she said.

"I'm so sorry, but Italy works sometimes," said Lorenzo Robustelli, a spokesman for the Roman agency coordinating this year's Jubilee, or Holy Year, celebrations.

Behind the effort was a keen awareness that much of the world's attention would be focused on Italy and Rome--site of the Vatican, the center of Roman Catholicism--at celebrations marking the anniversary of Jesus's birth.

"The fear was very real," said Mariella Gramaglia, deputy director general of Rome. But special attention was paid to the electrical system, which "could have had a domino effect on the traffic lights, on the telephone system, water. Everybody worked well."

A spokesman for the rail system, Gianni Farnetti, said that "Italians are skeptical, and we said . . . nothing's going to happen. But we couldn't take the risk," and so all the trains were halted at midnight as a precaution and restarted gradually.

As Italy reopened for business today, few problems of any consequence were observed. Computers extended the jail terms of some prisoners in Venice and Naples by 100 years; some employee timecards were mis-stamped; 2 percent of the country's automatic teller machines went on the fritz; 20 small towns reported computer-related "inconveniences and difficulties" out of several thousand queried by the federal government.

"We were really impressed--no, really unimpressed. Everything worked just fine; we were just a little bit let down by the hype," said U.S. Air Force Capt. John Haynes, a spokesman for the NATO airbase at Aviano in northern Italy.

Leggio, the country's Y2K chief, warned that not all the troubles will surface immediately, and some may never surface at all. Italian companies "have no interest in publishing their malfunctions if they have no impact on their customers," he said. "They repair it in silence. This is natural. . . . So there will probably be a big set of problems which are repaired inside the companies," particularly those traded on stock markets.

Leggio and Falconi both said the crisis centers will be maintained in some form until March, by which time they hope that computers will have coped with another potential computer bug--the fact that 2000 is a leap year. "A state of caution is being maintained at a high level for the eventuality that abnormalities could occur," the government said today.

Special correspondent Sarah Delaney contributed to this article.

CAPTION: Runners carry a banner as they start a New Year's marathon in Rome. Italians were relieved that their Y2K glitch fears were unrealized.