Medicare calls the paperwork EOBs -- explanation of benefits.

But when the "This is not a bill" notices are sent to the wrong person month after month after month, some recipients might be tempted to refer to them with another set of initials.

"Why can't they put a stop to this?" said Thelma B., an 83-year-old retired nurse. She was visibly upset as she recounted everything she has done to resolve the problem. "This is so upsetting."

"Medicare has really screwed this up," said her husband, Edward, 86, a retired electrician.

Since last September, Mrs. B. has received Medicare paperwork that should have been sent to another woman who has the same first and last name. Although the women have different middle initials, it hasn't helped untangle the mess.

To compound the problem, several of the notices include -- on the same pages -- treatments provided to Mrs. B. and treatments provided to the other woman. Fortunately for Mrs. B, her health problems aren't as serious as the other woman's.

Because the other woman is being treated at local hospitals, Mrs. B. believes she lives in the area, but hasn't been able to locate her.

When Mrs. B.'s phone calls and letters to Medicare failed to correct the problem, she called me.

I drove to a retirement community in the South Hills where Mrs. B. and her husband share a one-bedroom apartment. She had all the paperwork neatly set out on a table.

"Look at all this," she said. "Can you believe it?"

There are more than 38 million people receiving Medicare benefits, according to data compiled in 2006. There have to be any number of people with the same first and last name, and even the same middle name.

It isn't clear what has happened here, but it could be as simple as the ubiquitous "computer error" that has caused Mrs. B. such anguish.

"If I'm getting her paperwork, is she getting mine?" Mrs. B. asked. "That information is supposed to be confidential."

Mrs. B.'s daughter, Janet J., a registered nurse who has worked in the health insurance industry for 20 years, said she was able to confirm that the other woman was being treated at a local hospital that was identified on the paperwork her mother had received.

Janet J. called the hospital and explained her mother's problem to a woman in the billing department. She said the employee was sympathetic but said the hospital couldn't do anything because it was billing Medicare for the other woman's treatment and being paid for it.

Janet J. called Medicare.

It was "an extremely frustrating experience," she said.

"I told them I was trying to help them correct a problem," she said. "I told them they obviously were doing something wrong because my mother was getting all this paperwork that belonged to someone else. I talked to a front line person, was placed on hold for an extended period of time and then spoke a supervisor. They were no help at all. None.

"Medicare is releasing private insurance information in violation of HIPAA," she said, referring to the Health Insurance Portability and Accountability Act. "If federal and state agencies find out about this, they could come down real hard on Medicare. What is it going to take to get this cleared up, a lawsuit?"

That won't be necessary, said Lorraine Ryan, a Philadelphia-based spokeswoman for the Centers for Medicare & Medicaid Services, the agency that oversees Medicare.

She said she understands the frustrations of Mrs. B. and her daughter. "I wouldn't want anyone opening my mail, either," she said.

Ms. Ryan said she wanted to assure Mrs. B. and the other woman that the mix-up wouldn't adversely affect their medical benefits. "Their benefits aren't in jeopardy," she said.

Ms. Ryan said her agency has asked one of its subcontractors to find the problem and correct it.

Mrs. B. agreed to forward photocopies of all the paperwork she has received since September.

"I hope that will resolve all this," she said.