At the University of Michigan Health System, one of the first to experiment with full disclosure, existing claims and lawsuits dropped to 83 in August 2007 from 262 in August 2001, said Richard C. Boothman, the medical center’s chief risk officer.

“Improving patient safety and patient communication is more likely to cure the malpractice crisis than defensiveness and denial,” Mr. Boothman said.

Mr. Boothman emphasized that he could not know whether the decline was due to disclosure or safer medicine, or both. But the hospital’s legal defense costs and the money it must set aside to pay claims have each been cut by two-thirds, he said. The time taken to dispose of cases has been halved.

The number of malpractice filings against the University of Illinois has dropped by half since it started its program just over two years ago, said Dr. Timothy B. McDonald, the hospital’s chief safety and risk officer. In the 37 cases where the hospital acknowledged a preventable error and apologized, only one patient has filed suit. Only six settlements have exceeded the hospital’s medical and related expenses.

In Dr. Das Gupta’s case in 2006, the patient retained a lawyer but decided not to sue, and, after a brief negotiation, accepted $74,000 from the hospital, said her lawyer, David J. Pritchard.

“She told me that the doctor was completely candid, completely honest, and so frank that she and her husband  usually the husband wants to pound the guy  that all the anger was gone,” Mr. Pritchard said. “His apology helped get the case settled for a lower amount of money.”

The patient, a young nurse, declined to be interviewed.

Mr. Pritchard said his client netted about $40,000 after paying medical bills and legal expenses. He said she had the rib removed at another hospital and learned it was not cancerous. “You have no idea what a relief that was,” Dr. Das Gupta said.