When the doctors in training who help staff Children's National Medical Center were negotiating for better benefits and working conditions last year, the hospital administration eventually gave them a take-it-or-leave-it offer and pointedly noted that the hospital had no legal obligation to deal with the residents' union, doctors said.

The next time the residents negotiate a contract, the balance of power won't be so lopsided.

By ruling that residents at private hospitals have the right to unionize and bargain collectively under federal labor protections, the National Labor Relations Board this week strengthened the hand of physicians in training, potentially shifting the economic underpinnings of the nation's teaching hospitals.

Residents, who have graduated from medical school to become clinical apprentices, routinely put in 80-hour work weeks for about $9 an hour, handling responsibilities that range from the most menial medical chores to the most sensitive surgical operations. The strain takes a toll on their lives, and some say it isn't good for patients.

But for a variety of reasons, many people in the medical world said teaching hospitals are unlikely to become battlefields of union activism.

"I think in most cases it'll be business as usual," said Gerard F. Anderson, director of the Johns Hopkins Center for Hospital Finance and Management.

Part of the explanation is rooted in the professional ideals of the young doctors.

"I just think it would go against the Hippocratic Oath to strike," said Katherine Widnell, a neurology resident and president of a council that represents residents at Johns Hopkins Hospital in Baltimore. "I think the threat of striking is something that would be very hard to justify when it would be patients who suffer."

Amy Burke, a resident in internal medicine and pediatrics at Georgetown University Medical Center, said she worries that the NLRB ruling could establish "an atmosphere of antagonism and distrust" between residents and their employers. "My feeling is, I didn't get in this for the money, and this is part of my training, and as long as it's done in a safe manner I don't need a union," Burke said.

If residents try to flex their new muscle, they could find that it isn't as strong as it appears.

Though residents are a source of cheap labor for hospitals, they are also an expense, because they require faculty instruction and supervision and tend to order more tests than veteran doctors, analysts say. If residents demand much higher salaries, hospitals could try to replace them with more experienced physicians and scale back their teaching programs, hospital experts said.

If residents held out for $40 an hour, for example, "you may be able to afford one quarter the number . . . and the rest of the residents could suddenly not have any place where they could complete their training," said Catherine DeAngelis, a vice dean at the Johns Hopkins University School of Medicine.

Without the experience of a residency, doctors could not become board certified in their specialties "and nobody is going to hire them," DeAngelis said.

The troubled financial condition of many teaching hospitals would make it difficult for hospitals to grant residents major concessions, hospital representatives said.

Then there's the simple reality of life as a resident: Working flat out in a hospital and studying medical texts leave little time for union activity. The rapid turnover of residents compounds the challenge: Most move on to new jobs within several years.

Still, the NLRB ruling could give residents added influence over a range of issues that go beyond wages and working hours.

Jordan J. Cohen, president of the Association of American Medical Colleges, said he is worried that the evaluation and promotion of young doctors could become subjects of collective bargaining and binding arbitration.

In interviews, residents said their priorities in collective bargaining include day care for their children, health benefits for their families, and better sleeping quarters when they spend nights on call.

Unions could make it easier for residents to call for change, said Sameer Bade, president of the residents' section of Med Chi, the Maryland medical association. "The culture of residents' training has been such over so many years that you typically don't speak out," Bade said. "I think a lot of people don't complain about poor working conditions or being overworked because they're afraid of the impact on their evaluations."

Even without the ability to strike, a union at the University of Michigan Health System last year helped residents obtain retirement benefits--payments equal to 7 percent of their salaries--that are envied by residents elsewhere.