Many doctors will start advertising their fees and services now that the American Medical Association has said it is permissible, the main author of a new AMA code of ethics predicted yesterday.

The AMA House of Delegates voted in Chicago Tuesday to adopt a new code that drops an old ban on "soliciting" patients.

The AMA shift came in reluctant response to a 1979 Federal Trade Commission determination that the AMA's traditional ban on solicitation -- interpreted by local medical societies to include most advertising -- restrained competition.

Dr. James Todd of Ridgewood, N.J., chairman of the committee that wrote the new code, said in an interview he thinks not only that more doctors will advertise but also that "good" advertising can help control health costs by encouraging moderate fees.

In fact, doctors have been free to advertise since the FTC ruling. Some West Coast plastic surgeons, not always regarded as qualified by their more conservative colleagues, have openly claimed they can beautify patients.

But most physicians have advertised no more than they did before, except to expand in some cases the kind of "business card" ads or phone-book listings medical societies always permitted.

Dentists have begun advertising in fair number since the FTC ruling.

Now, said Todd, "the public is entitled to know how to make a legitimate choice between doctors" and various doctors' qualifications and fees, "and I hope this occurs."

Among fees that might be advertised are those for surgical operations and for health checkups, he suggested. "I think it would be difficult to give a real idea of the cost of caring for some medical conditions," he said. "And we'll continue to be concerned about ads that make claims a physician can't support. You can't promise any patients a good result."

At the same time, he said, doctors can tell patients about their professional certifications, and this plus fee advertising by both help control fees and "help patients understand" why some physicians charge more.

Dr. Lowell Steen, chairman of the AMA's board of trustees, took a different view. He said he thinks "there may be some increase in advertising," but mainly "not from the top-notch physician but from those doing deceptive advertising."

"A problem the profession faces," Todd agreed, "is that we no longer have the power to severely discipline those who go beyond bounds. We can only rely on peer pressure and state licensing agencies."

In another change, the AMA voted to let physicians refer patients to chiropractors.The AMA has been hit by lawsuits in which chiropractors charge that the AMA has hurt their practices, lawsuits costing it more than $1 million a year to defend.