Parking lot owner turned real estate investor, Dominic F. Antonelli Jr., one of the dominant figures in Washington business, yesterday declared personal bankruptcy and set in motion a court-supervised reorganization of his finances.

Antonelli, 68, became the biggest local developer whose finances have collapsed under the weight of risky investments and bank loans piled on during the the real estate boom of the 1980s.

"It's obviously very stressful for him, but I think he's doing extremely well," said Antonelli's lawyer, Roger Frankel. "He feels he has not done anything wrong and still hopes to come out of this paying everyone off and keeping a reasonable estate for himself."

Antonelli's lenders -- which include American Security, Maryland National, Riggs, First American, Sovran, Chase Manhattan and other banks already shaken by delinquent real estate loans -- may emerge from the bankruptcy process with only a fraction of the money they are owed, real estate executives and others familiar with Antonelli's problems said.

As of last spring, when real estate values were generally much higher, Antonelli owned interests in real estate projects that were valued at $1.8 billion and carried loans of $1.3 billion, according to a financial statement. As of last summer, he was personally liable for debts of about $550 million to three dozen lenders.

Antonelli made his money beginning in the 1940s by gradually, conservatively developing office buildings on the downtown real estate held by his Parking Management Inc. He lost it by investing in far-flung, highly speculative development projects managed by other developers, and by cosigning loans for them over the past decade.

If Antonelli had quit while he were ahead, he would have been the model of the self-made millionaire. The grandson of a stonecutter and the son of an olive oil importer, he delivered newspapers and parked cars in downtown Washington as a teenager during the Depression. Sometimes, he had nothing to eat but cornflakes.

When he went to change money at the Mayflower Hotel, the staff would chase him away because of his dirty clothes. He never finished high school.

Many years later, Antonelli built his corporate headquarters on the DeSales Street NW site where he once parked other people's cars, and along with other investors he bought the Mayflower. He said he was worth $164.1 million last spring -- or only $44.8 million if he were forced to sell his holdings immediately -- and by that time his fortune was in decline.

Now, a bankruptcy judge will decide what becomes of investments he accumulated over a lifetime, including a 103-foot yacht, a secluded 24-acre Potomac estate, small interests in the Hollywood movies "Raising Arizona" and "Miller's Crossing" and a 50 percent interest in the Natural Bridge, the geologic formation in Southwestern Virginia once owned by Thomas Jefferson and known as one of the "Seven Natural Wonders of the New World."

Although the bankruptcy may erase Antonelli's wealth, it cannot erase his considerable mark on Washington.

Beginning in the late 1940s, he bought property throughout downtown Washington, razed old buildings and converted the real estate into commercial parking lots. In time, he put up office buildings on the parking sites or leased them to other builders for them to develop, making much more money. The process hastened the transformation of residential neighborhoods into commercial districts.

Antonelli's many early real estate purchases put him in an almost unparalleled position to profit as the Washington area grew and land values rose. Along the way, a close partnership with Kingdon Gould Jr., a wealthy descendant of 19th century financier Jay Gould, helped solidify his position in the Washington business establishment.

The firm Antonelli built, PMI, went on to control more than a third of the parking spaces in the city. Congress protected his franchise by prohibiting the D.C. government from operating competing municipal parking lots. Antonelli and his associates successfully lobbied to preserve the prohibition.

Antonelli helped found Madison National Bank in 1963. Madison became a source of loans for him, and he served on the Madison board of directors until last year, when troubled loans forced him to resign.

Antonelli's business interests sometimes revolved around the federal and District governments. Government workers parked in his lots and worked in his buildings.

In the late 1970s, Antonelli was convicted of bribing a D.C. official to obtain a government office lease, but the verdict was set aside on appeal. Antonelli won acquittal in 1979 at a second trial, which was moved to Philadelphia because of all the publicity the case had received here.

Even before that ordeal, Antonelli shunned the press and public attention. Through his lawyer, he has declined repeated requests for interviews since his financial troubles came to light.

Antonelli's friends and business associates, many of whom have profited from their association with him, talk about the developer with reverence. They describe him as a devout supporter of the Catholic church and various charities. They say his word is his bond. They praise his business acumen, even in the face of his failures.

After years of more cautious, controlled growth, Antonelli got into financial trouble by bankrolling several other developers during the 1980s.

Through those alliances with friends and business acquaintances, Antonelli's holdings, once concentrated in downtown Washington, grew to include interests in about 165 apartment houses, office buildings, hotels, tracts of land, residential developments, warehouses, shopping centers and other properties from Pennsylvania to Florida and points west.

Many of the ventures failed. The papers Antonelli filed yesterday at the federal bankruptcy court in Rockville did not say how much he owes altogether or how much his holdings are worth. Sources said it would be difficult to put a value on Antonelli's investments due to their complexity and the depressed state of the real estate market.

For months, Antonelli had been negotiating with creditors in an attempt to reach an out-of-court settlement. The effort broke down last month when five creditors asked the bankruptcy court in Rockville to declare Antonelli bankrupt.

Before the five creditors went to court, other lenders had concluded that allowing Antonelli to get some benefits now would be a was a small price to pay to avoid a costly and potentially protracted bankruptcy proceeding. The legal expenses associated with a bankruptcy could add as much as $20 million to the cost of an out-of-court settlement, and it could take the bankruptcy court a minimum of six years to work out a solution to Antonelli's complicated financial problems, according to Thomas H. Speed of First Union National Bank of North Carolina, who had chaired an informal creditors' committee.

"We could come back sometime in the next century and still be talking about this," Speed said.