HANOVER, N.H. - Six health-care systems serving more than 10 million patients around the country have begun sharing data in hopes of helping other providers improve quality while reducing costs.

The project announced Wednesday brings together the Cleveland Clinic; Denver Health; New Hampshire's Dartmouth-Hitchcock Medical Center and an affiliated health institute, Geisinger Health System in Pennsylvania; Intermountain Healthcare in Utah; and the Mayo Clinic in Minnesota.

Although several of the groups have been cooperating for years, the new collaboration represents the first time they have shared so much information or turned it around so quickly.

Starting with knee replacements and moving on to other conditions and treatments, the participants will analyze the data and then spread the word about which approaches result in the best outcomes at the lowest costs. The goal is to spend six months on each condition, then move on, said James Weinstein, director of the Dartmouth Institute for Health Policy and Clinical Practice.

"The health care [airplanes] that we're currently flying with no instruments are crashing,"Weinstein said. "This is going to put some instruments on the plane to show America how we can move forward."

The group plans to focus on conditions and treatments for which costs have been increasing rapidly and for which there are wide variations in quality and outcomes. Knee replacements, for example, are performed more than 300,000 times a year in the United States with costs that range from $16,000 to $24,000 per surgery. Other targets are diabetes, heart failure, asthma, weight-loss surgery, labor and delivery, spine surgery, and depression.

Weinstein said more than 30 other health organizations expressed interest in joining, but leaders decided to start small. He expects other health-care providers will note the results given the big names involved, as will insurers and employers struggling to cover their workers' costs.

Weinstein said he hoped the federal health-care overhaul would lead to federal funding for the project but said the partners would proceed without it.

"A lot of the legislation really deals with, at least initially, insurance reform," he said. "It doesn't really talk about the patient. What we've really been interested in is the patient, and how we actually effect change that improves the care for the patient and the population, not just about health care but to be healthy."