LOS ANGELES, FEB. 25 -- An unprecedented survey by the Hemlock Society in California has fueled the national debate about euthanasia, finding 79 doctors who say they have intentionally taken the lives of terminal patients who asked to die.

Dr. James Todd, deputy executive vice president of the American Medical Association, which opposes active euthanasia, said he knows of no other significant effort in this country to determine how many doctors secretly perform such acts.

Twenty-nine of those who said they helped patients die acknowledged doing it more than three times, and 20 of them volunteered their names, although the society's executive director, Derek Humphry, destroyed their questionnaires Tuesday on the advice of attorneys.

The ethical and legal controversy over mercy killing by doctors has erupted in editorials and sermons throughout the country since publication of a letter in the Journal of the American Medical Association Jan. 8. In it, an anonymous doctor recounted giving a 20-year-old dying cancer patient a fatal dose of morphine.

Chicago prosecutors have been granted a subpoena demanding information that would identify the letter writer, and the AMA is resisting it under an Illinois law permitting journalists to protect confidential sources.

The mail survey by the Hemlock Society, a 24,000-member organization promoting what Humphry calls "the right to choose to die," stemmed from a campaign by a sister organization, Americans Against Human Suffering, to change California law to allow patients to receive on demand a quick, peaceful death.

"The leaders of the medical profession have been saying that not many doctors believe in this, that you will not get many doctors to do it even if you do pass the law," Humphry said.

Humphry said one national polling organization declined to do the society's survey, saying that not enough doctors would respond. The society spent $6,000 to hire a local polling firm and send 5,000 questionnaires to doctors practicing general medicine, cancer treatment or care of the aged. It received 588 responses.

Passive euthanasia -- withholding life-preserving treatment and even nutrients from some terminal patients, including those with no brain activity -- has some support in law and is endorsed by the AMA. But active euthanasia, such as giving a fatal dose of narcotics, is illegal nationally and opposed by the AMA.

Todd, after reading the survey, said he was not sure that doctors who reported performing euthanasia meant the active form. Nevertheless, he said, the survey indicated that their numbers were "very, very, very few."

Humphry noted that the questionnaire asked whether physicians had used "active steps" to terminate a patient's life. Fifteen said they had done so once, 35 two or three times and 29 more than that. Among the 79 doctors, 84 percent said they think that they acted properly, while 16 percent said they did not.

Humphry emphasized that 62.4 percent of the 537 doctors who answered other questions on the survey said they think that it is "sometimes right" for a doctor to help a terminally ill patient die.

This, he said, showed that the euthanasia referendum now collecting signatures for the November ballot would have medical support if approved. In a Louis Harris poll of 200 physicians last year for the Harvard Community Health Plan, 66 percent opposed active euthanasia and 30 percent supported it.

Ten of the doctors in the Hemlock survey who said they took active steps to terminate a patient's life also said they are members of the Roman Catholic Church, which forbids euthanasia.