WALNUT CREEK, Calif. (AP) _ A teen-age boy's shotgun wound was simulated but the perspiration on brows of judges watching the film was real when the sixth biennial John Muir Medical Film Festival opened Monday.

The festival, running through Saturday, drew more than 400 film and videotape entries from the United States and nine other countries.

''A well-crafted film can get more information to health professionals than a journal article,'' said festival director Chip Bissell. ''For some surgical techniques, there is no better way to teach it than on film.''

One compelling entry was the winner in the emergency medicine category, titled ''Shotgun Wound to the Abdomen: Stabilization of Patients in Shock.''

That entry, using a $15,000 computerized laserdisc video, puts the viewer in the place of a doctor in a hospital emergency room where a 16-year-old boy has just been brought in with blood gushing from his stomach. The viewer must use the device to guide nurses and technicians through emergency procedures. If the proper steps are not taken, the patient dies on screen.

''I could literally see the sweat on the faces of the judges as they viewed the film,'' Bissell said. ''I'm not a health professional, and I lost my patient in six minutes.''

He said the film demonstrates ''the kind of hands-on care of a patient that you can't get from a journal article.''

Entries this year include the first ever from Eastern Europe, a Hungarian documentary addressing ethical issues presented by blood donations. There also is a new category devoted to films about AIDS.

Successful films can earn as much as $500,000 in sales to hospitals and medical schools, Bissell said. Winning films are described in a festival catalog for which John Muir Hospital has received more than 50,000 requests.