More than 1,200 nurses walked off their jobs yesterday at Washington Hospital Center in a contract dispute that strikers said was triggered more by union objections to mandatory overtime rules than by demands for higher wages.

Hundreds of D.C. Nurses Association members took to the streets at 5:30 a.m., chanting and carrying signs at Irving and First streets NW. They said their primary goal was to gain greater influence over hospital policies that affect the quality of patient care.

All day long, passing cars and trucks sounded their horns in support, and the nurses cheered in return. It was the first strike at the region's largest medical facility since 1978, when nurses walked out for 31 days.

Inside, city officials and hospital executives reported no significant service disruptions. A spokeswoman for MedStar Health Inc., the Columbia-based nonprofit that owns the 907-bed facility, said the workload was heavier than usual.

Filling in were 625 replacement workers from across the country and 250 nurse managers who returned to direct patient care, said Lisa Wyatt, the hospital's vice president of public affairs.

The hospital contracted with Denver-based U.S. Nursing Corp. to provide the replacements. That company specializes in staffing strikebound hospitals with outside nurses during work stoppages.

"Everything is going unbelievably smoothly," Wyatt said. "One of our physicians told the medical director that it's actually going better than usual."

Wyatt said the hospital had 741 inpatients yesterday and that surgeons performed about 35 operations, including 11 heart operations, in addition to about 50 cardiac catheterizations.

"We have seen no change in terms of admitting patients here," Wyatt said. "We want our nurses to return as quickly as possible, but we are prepared to keep this hospital operating on a business-as-usual basis until the strike is settled."

The striking nurses complained that management has abused its power, solving persistent scheduling problems in the operating rooms and other units by requiring nurses to stay on for overtime shifts. Nurses said hospital managers do this partly because Washington Hospital Center, like hospitals nationwide, suffers from a chronic shortage of available nurses.

"These nurses are tired," said Ramona Gonzalez, a 20-year veteran of the hospital. "They want their benefits. They want their holiday and vacation time."

Gonzalez said the nurses want a program restored that would allow them to work weekends only, putting in two 12-hour shifts.

Bargaining broke off late Tuesday, and no other meetings have been scheduled, according to officials from both sides.

The hospital has offered the nurses an aggregate raise of 16.5 percent over three years and a limit on mandatory overtime to two shifts every six weeks. Wyatt said the nurses want raises of 22 to 28 percent over the three years.

The union, though, said it has asked for a wage increase of 20 to 22 percent over three years, plus tighter restrictions on required overtime; only in emergencies would nurses be forced to stay on after their shift.

Washington Hospital Center said its offer compares favorably with raises accepted by the D.C. Nurses Association for other hospitals in the past year. Under the expired contract, the average nurse at Washington Hospital Center collects $60,626 a year, including base pay, bonuses and overtime.

On the picket line, nurses complained that hospital officials have refused to give them a voice in setting hospital policies. "They're not interested in our input or heeding our alarms," said Sharon Clark, an emergency nurse who has worked at the hospital for 25 years.

She said the nursing shortage has forced the hospital to assign recent nursing school graduates as supervisors and left some nurses overwhelmed with too many patients to care for.

D.C. Health Department Director Ivan C.A. Walks said the replacement nurses began months ago to apply for temporary licenses to practice in the District. So far, he said, the city has issued 700 such permits.

"All the nurses are D.C. licensees and working legally," he said. Any complaints or concerns about the quality of care in the hospital are investigated immediately by two Health Department officials who are stationed in the hospital, Walks said.

Clark said she bears no ill will toward the replacements. They are to be paid an average of $2,700, plus expenses, to work five 12-hour days a week. Some specialized nurses will get as much as $5,000.

"I'm not angry," Clark said. "I'm a little disillusioned. For [the replacement workers], it's a personal necessity. I'm hoping they're as competent as the nurses who are striking."

The local nurses have no strike fund, but union officials said the job action could go on for a long time because nurses are always in demand for temporary work--even while they strike.

"It's difficult for nurses without benefits," said union official Gwen E. Johnson. "Staying out longer will be a financial challenge, but there are options."