The myth began in the small community of Framingham, Mass.

There, in the late 1940s, a sweeping, government-funded study began to track the cardiovascular health of thousands of men and women, noting what they ate, how they lived and from what they died.

Early in the now-famous Framingham Heart Study, researchers noticed that men began suffering heart attacks in middle age, while women seemed unaffected. The experts guessed that because women have high levels of the hormone estrogen, they were protected against heart disease.

"The early conclusion from that study was that women were not suffering from heart attacks, that women are immune due to estrogen," says Dr. Edward B. Diethrich, medical director of the Arizona Heart Institute and author of the new book "Women and Heart Disease."

That explanation was accepted as fact. Two decades later, while in medical school, Diethrich recalls a professor telling him: "Don't worry about women."

Wrong.

Physicians now recognize that while estrogen--or something--does seem to protect most women against heart disease in the first half of life, after menopause the rate of heart disease soars in women and is almost equal to the rate in men by age 65. For example, men age 65 and older suffer an estimated 440,000 heart attacks each year, compared to 374,000 in women age 65 and older.

But many women still do not get prompt diagnosis and treatment of heart disease, experts say. And many women have failed to educate themselves about the risks and warning signs.

"If you ask doctors what the biggest killer of women is, I think a lot of doctors would give the wrong answer," Diethrich says. Heart disease is the leading killer in women, accounting for 240,497 deaths in 1989, the last year for which statistics were available.

"And most women don't realize that once you are post-menopausal, the risk is equal (to men)," he says.

Many of the studies on heart disease have been done on men, leaving physicians with a serious lack of understanding of the disease in women, Diethrich says.

He tells two stories to illustrate the persistence of the myth: In one case, a woman came to an emergency room four times complaining of chest discomfort. Her complaints were dismissed as stress-related. It's "nerves," she was told.

The next time the pain hit, she didn't make it to the emergency room--and she died, Diethrich says.