Yet even with all of its effort, its chairman and chief executive, George C. Halvorson, acknowledges Kaiser has yet to achieve the holy grail of delivering that care at a low enough cost. He says he and other health systems must fundamentally rethink what they do or risk having cost controls imposed on them either by the government or by employers, who are absorbing the bulk of health insurance costs. “We think the future of health care is going to be rationing or re-engineering,” he said.

Mr. Halvorson is convinced that Kaiser’s improvements in the quality of care save money. But he also says that the way to get costs lower is to move care farther and farther from the hospital setting — and even out of doctors’ offices. Kaiser is experimenting with ways to provide care at home or over the Internet, without the need for a physical office visit at all. He also argues that lower costs are going to be about finding ways to get people to take more responsibility for their health — for losing weight, for example, or bringing their blood pressure down.

“The obesity work is incredibly difficult,” he said. “It’s very, very hard to move the needle.”

Other health care experts say that while Kaiser has a place in the future, whether it is the best model for the country’s health care remains unclear. “They have not translated some of their strengths into better prices,” said David Lansky, the president and chief executive of the Pacific Business Group on Health, which represents employers on the West Coast, many of whom purchase coverage from Kaiser for their workers.

And there are other concerns, such as whether an all-encompassing system like Kaiser’s can really be replicated and whether the limits it places on where patients can seek care will be accepted by enough people to make a difference. Or whether, as the nation’s flirtation with health maintenance organizations, or H.M.O.’s, in the 1990s showed — people will balk at the concept of not being able to go to any doctor or hospital of their choice.

“The more you restrict the patient’s ability to do what they want, you risk reigniting the backlash we had in the past,” Mr. Lansky said.