AMERICANS more than just believe the health information they get from fictional television shows. Spurred by what they see on shows like "ER" or "The Bold and the Beautiful," surveys suggest, they take action. They go to the doctor. They tell a friend to have that cough checked. They ask a lover to use a condom.

Fans develop trusting relationships with the characters who come into their homes each week, and industry insiders can't betray that trust. "I'm aware of the number of people who are paying attention to the facts around the fiction," says Jan Nash, executive producer of "Without a Trace." Thanks in part to the Internet, where health sites consistently rank at the top of those most visited, more and more viewers know when something doesn't ring true.

They're getting a lot of chances to make such calls. Science is invading scripts. Disease is increasingly a backdrop to plots. The woes of the nation's healthcare system are punch lines. Heroic characters have mental diseases or incurable neurological disorders.

And behind the scenes, a body of communications research and an eager network of health and policy advocates are working with writers and producers to get the facts right. The shows milking medicine for back stories or main plot lines aren't limited to the medical genre such as "ER," " Grey's Anatomy" or " Scrubs." Sick, damaged or dying characters are showing up in shows about crime, politics, the legal profession, or wacky families and friends.

But seeing how profoundly true prime-time television can be was a shock, nonetheless, for Robert T. Brennan, a statistician at the Harvard School of Medicine and his daughter, Emma Brennan-Wydra, 13. On Jan. 3, 2006, they thought the night was winding down like hundreds of others, just another evening of TV viewing in their Somerville, Mass., home. It was 10 p.m., and Emma, a devotee of "Law & Order," was curled up watching the episode "Infected" with her father. "No popcorn. Nothing special, just uneventful viewing," says Brennan.

Little did they know, within their pajama-clad coziness on the other side of the country, that they were about to get an insider's glimpse into one of the latest trends in Hollywood.

Brennan and his daughter sat, mesmerized as the crime drama got closer and closer to home. It was about a grammar school-aged boy who, after seeing his mother shot to death, killed her murderer and went on trial as an adult.

"Annie Potts is addressing the jury," Brennan says, still amazed that his study, published in the May 27, 2005, journal Science, was quoted, statistic by statistic, by actress Potts, who played the boy's defense attorney, Sophie Devere. "She talked about kids being two to three times more likely to commit gun violence after they've been exposed to gun violence." As the character gave closing arguments, she referred to Science, gave the number of study participants and said the research took place in Chicago. There was no doubt. She was talking about Brennan's study.

"Emma and I looked at each other in total disbelief. Literally, I was flushed and my hair was standing up on my neck. The exact details of the study were on television," says Brennan. "And the accuracy of it was really amazing. I hate to say this, but it was more accurate than anything I've ever had covered in a newspaper."

His research ended up on the airwaves after Dr. Neal Baer, pediatrician and executive producer of "Law & Order: SVU," read the study on childhood violence by Brennan and coauthors Jeffrey Bingenheimer and Felton Earls. With all due respect, the paper was "wonky policy stuff, research that almost nobody reads," says Baer. But for a doctor who is also a television writer, it triggered an idea for a plot. "Just as you're exposed to flu when someone sneezes on you, this boy was exposed to violence. He was infected, and he committed a violent act," Baer says of his TV character.

What Baer did with a dry study illustrates the challenge to television writers: Take timely, important topics and make them entertaining. Accuracy and responsibility matter, industry insiders say, but their job is to attract and hold television viewers, not lecture or teach.

"Ultimately, our responsibility is to the drama of the show," says Nash. If writers start getting preachy, she says, viewers will hit the button on the remote.

At a time when reliance on traditional news media is slipping, entertainment communication becomes an important health issue. Prime-time television is where Americans gather, and it's where they learn. It makes sense to put the information where people are likely to get it.

The emphasis on the human and emotional drama behind the science, it turns out, is exactly what helps messages stick with viewers, according to communications research. Movies have a powerful effect too, but television fans come to know the characters they watch each week. Done well, the messages play out in the lives of familiar characters, and viewers learn something.

Premiering a theory

One of the first proofs that popular shows can educate large numbers of people came in 1977, in Mexico. Broadcast pioneer Miguel Sabido decided to make use of a classic learning theory, called social cognitive learning, in a soap opera. The theory, developed by Stanford social scientist Albert Bandura in 1961, holds that one way people learn is from watching others, particularly if they identify with the people and observe long enough to see a successful outcome. Sabido's telenovela was called "Acompaname," or "Accompany Me." The characters, including a poor but strong young woman who had two children and didn't want any more, grappled with family planning.

In its first year, it was apparent that the people who listened also learned -- and acted. The Mexican government's National Population Council reported that monthly phone calls requesting family planning information increased from next to none to 500. Contraceptive sales increased 23% the first year the show aired, compared with an increase of 7% the previous year.

Following Mexico's success, the entertainment-education movement spread to India, China and Africa, where people in even the most remote villages tune their portable radios to soap operas. Characters routinely deal with the reality of AIDS. "You put up a billboard saying 'AIDS Kills, Use a Condom,' and it doesn't tell a woman how to approach her husband to talk about condoms," says Sonny Fox, whose Studio City consulting company works internationally to advise media and public health advocates. "In a radio drama, you put that right into the story. The listener has to be able to say, 'If she can do it, I can do it.' "

At a recent workshop in Johannesburg, South Africa, a survey presented Nov. 6 by researchers from Johns Hopkins Bloomberg School of Public Health examined the effect of one such program. It found that reported condom use during the last sexual encounter increased from 34% among people who did not tune into a soap opera called "Tsha Tsha" to 60% among those who watched 10 or more of the programs.