One-fourth of patients with health problems in five countries say they have suffered from a medical mistake or prescription error in the past two years, a Harvard-led study reports in an issue of Health Affairs published Monday.

Medical errors have been a hot topic the past three years, since the Institute of Medicine estimated that mistakes may kill 44,000 to 98,000 Americans annually.

The latest report shows that the problems persist in countries with widely different health systems -- and that they get worse the more doctors a patient sees.

Of those who visit three or more doctors a year, the study found, one in three surveyed said they had suffered from a medication or medical error.

''The biggest risk is when you're seeing multiple doctors who are doing lots of tests and prescribing a lot of drugs,'' said Robert Blendon, the Harvard professor who led the study. ``It's lack of coordination. If you're taking Coumadin [a blood thinner] given by one doctor, then maybe you shouldn't be taking another drug given by another doctor.''

Last week, the Florida Legislature, attempting to cut down on medical errors, passed a bill ordering doctors to improve their handwriting, so that pharmacists and nurses could do a better job of reading prescriptions.

''Certainly, the problem isn't just a doctor's handwriting,'' said Karen Davis, president of the Commonwealth Fund, a healthcare research group that funded the study.

She and other experts say the solution is to track patients more closely with computers.

Arthur Palamara, a Broward surgeon, said doctors had a responsibility to make their writing legible but doubted that that could be done by legislative fiat.

''It certainly would be impossible to give all the doctors in the state penmanship tests,'' he said.

Palamara said Memorial Regional Hospital in Hollywood, where he practices, hoped to have a computerized prescription system in place by next year.

The Harvard survey of sick adults was conducted in the United States, Canada, the United Kingdom, Australia and New Zealand. At least 750 persons were surveyed in each country.

The United States had the highest portion reporting errors -- 28 percent -- and the United Kingdom the fewest, 18 percent. But in all five countries, those who went to more than two doctors complained of errors almost twice as much as those who went to just one or two physicians.

Computerization of a person's prescriptions, Blendon said, would help cut down on mistakes.

''The system,'' he said, 'can start kicking things out: `That dosage doesn't make sense for that illness,' or 'that drug can't be given with that other drug,' or just a list of what drugs a person is allergic to.''

Computerization also would help, experts say, because doctors are sometimes rushed and don't refer to patients' medical records before writing prescriptions.

Blendon said the survey showed a crying need for case managers, too, for those who see more than two doctors a year. Managers not only could help reduce errors but also could help cut costs.

''This is only 10 percent of patients,'' he said, ``but they're an expensive 10 percent.''

The survey showed that more than one in four -- 28 percent -- of those who see more than two doctors in the United States and Canada said they were given duplicate tests by different doctors. And roughly a quarter in all five countries said they received conflicting information from different doctors.

Experts are still disputing the 1999 Institute of Medicine study, but many acknowledge that wrong doses of drugs may lead to several thousand deaths a year. Last year, a study found nurses who work long shifts or long workweeks likelier to make mistakes in dosages than those who don't.

In March, the Food and Drug Administration announced that it would demand that bar codes be placed on all medications used in hospitals. It is estimated that American hospitals will spend $7 billion to read the codes and computerize doctors' orders.