Tess Gerritsen and Michael Palmer, two of the biggest names in the medical-thriller genre, make it plain to the aspiring authors that their chances of success are small, but there is no shortage of physicians prepared to give it a shot.

"It's amazing how many of them are interested," said Gerritsen, whose best sellers include "Life Support," "Gravity" and "The Surgeon."

She said part of the reason may be the frustration that some doctors feel about a profession that seldom provides room for creativity.

"You're not supposed to be creative in medicine. You do what you're supposed to do and be objective and not make up things," she said, suggesting that those who look to writing "have this need to express another part of their brain."

Palmer, author of 10 books that include "Critical Judgment," "Natural Causes" and "Extreme Measures," said disenchantment about the way medicine is practiced is another catalyst that has doctors exploring other options.

"We've taken quite a pounding from managed care," he said. "Incomes have dropped, job satisfaction has dropped horribly, and there is so much pressure to conform to what bureaucrats think is good medicine."

Palmer, who lives outside Boston, keeps his hand in medicine, working 20 hours a week directing a program that helps physicians deal with illness or drug- abuse problems. Gerritsen, who fell in love with Maine during a vacation to Camden, moved there in 1990 and writes full time.

Doctors, of course, have pursued nonmedical writing long before Palmer and Gerritsen took up the craft. The most celebrated include dramatist Anton Chekhov, storyteller Somerset Maugham, Sherlock Holmes creator Arthur Conan Doyle and poet William Carlos Williams. Best-selling author Michael Crichton pioneered the techno-thriller.

Gerritsen, a California native, was a practicing internist in Hawai'i when she switched from medicine to writing, a change that allowed her to stay at home with her two young children. She wrote eight romantic suspense paperbacks for Harlequin before coming out in 1996 with "Harvest," her breakthrough medical thriller about the black-market trade in donor organs.

Palmer, a former internist who went on to become an emergency room doctor, was inspired by the success of Robin Cook, the ophthalmologist whose 1977 best seller, "Coma," is credited with creating the medical thriller genre. Palmer knew Cook when they were undergraduates at Wesleyan; they subsequently trained together at Massachusetts General Hospital.

The Medical Fiction Writing for Physicians program got its start when Steven Babitsky, who organizes conferences and seminars for doctors, approached Palmer with the idea. After Gerritsen agreed to team up with them, they scheduled the first program in September 2000.

More than 70 doctors attended, and enrollment grew to 120 in 2001 and 200 this year. Babitsky was so pleased that he launched a similar program this year for lawyers, taught by authors Lisa Scottoline and Stephen Horn. Both courses delve into the mechanics of writing, including plot and character development, back story, points of view and pacing.

In the medical program, Gerritsen and Palmer take a tag-team approach as they jointly lead all the writing sessions and take turns offering ideas.

While the program is not specifically focused on medical thrillers, it is that genre that most students have in mind.

"Evil drug companies, evil HMOs — they pretty much stick to medical topics," said Gerritsen, who pushes students to refine the premise of their story and look for ways to enhance its emotional force.