Zelda Rubinstein, the diminutive character actress with the childlike voice who was best known as the psychic called in to rid a suburban home of demonic forces in the 1982 horror movie "Poltergeist," has died. She was 76.

Rubinstein, who also appeared as the mother figure in a high-profile mid-1980s public awareness campaign in Los Angeles aimed at stopping the spread of AIDS, died today of natural causes at Barlow Respiratory Hospital in Los Angeles, said Eric Stevens, her agent.

Rubinstein was hospitalized at Cedars-Sinai Medical Center about two months ago after suffering a mild heart attack, Stevens said. "She had ongoing health issues and unfortunately they finally overtook her," he said.

A medical lab technician before launching her acting career in her 40s, the 4-foot-3 Rubinstein made her film debut as one of the little people in the 1981 Chevy Chase comedy "Under the Rainbow."

Among her other credits are the movies "Frances," "Sixteen Candles," "Teen Witch," "Anguish" and "Southland Tales" and the TV series "Picket Fences" on which she was a regular.

But Rubinstein made her biggest impact as Tangina in director Tobe Hooper's “Poltergeist,” co-written by Steven Spielberg, who also served as a producer.

"Do y'all mind hanging back? You're jamming my frequencies," Rubinstein's Tangina says as she tours the house after the young daughter has been sucked into a blinding white light in her bedroom closet and disappeared.

The role was written specifically for a little person.

"I thought it would be neat to show that someone's size had nothing to do with her psychic powers," Spielberg told The Times in 1982. "Good things can come in small packages, and that's certainly true of Zelda."

Film critics agreed.

Sheila Benson of The Times called Rubinstein's Tangina "the most original and reassuring character in the film."

The New Yorker's Pauline Kael raved that the "character gives the movie new life, and she makes a large chunk of it work. . . . she emanates the eerie calm of someone who is used to dealing with tricky, deceiving ghosts."

Kael added that Rubinstein was "so fresh a performer" that after she delivers a speech about the spirit world, "you want to applaud her exit line."

Rubinstein, who reprised her character in two "Poltergeist" sequels, expressed hope that "Poltergeist" would raise awareness of the little people in show business.

"Because I was born mouth first, it's natural for me to be a spokesperson," she said with a laugh in a 1982 People magazine interview.

Her activism began on the set of "Under the Rainbow."

"It's absolutely despicable," she said of the way the little people portraying Munchkins were used as comic relief in the movie. "You're not an actor if you're just a person that fits into a cute costume. You're a prop."

In the wake of "Under the Rainbow," she formed the nonprofit Michael Dunn Memorial Repertory Theater Company in Los Angeles. It was named after the late actor, a little person who received a supporting actor Oscar nomination for his role in the 1965 film "Ship of Fools."

Rubinstein's message to the 16 actors in her company, whose height ranged from 3 feet 8 to 4 feet 6, was: "Become an actor and your world will get much bigger."

The youngest of three children -- and the only little person in the family -- she was born in Pittsburgh on May 28, 1933. Her schoolmates called her Pigeon.

"There was something attached to the nickname that froze me," she told People.

In a 1992 interview with the Chicago Sun-Times, Rubinstein said she "had a rough childhood, [but] I became very verbally facile. . . . I learned to meet everyone head-on."

She was an adult before she was at peace with her small size. "I just decided it was a very interesting variation," she said.

Or put another way: "I just consider myself rather condensed."

Rubinstein won a scholarship to the University of Pittsburgh, where she earned a degree in bacteriology. She worked for many years as a lab technician in blood banks before giving up lab work for acting in 1978.

"I had to do something creative," she told People in 1982. "It was an internal feeling that I was sabotaging myself."

Her first agent would send her on casting calls for dancing soup cans and happy pumpkins.

"I couldn't and wouldn't do those parts, which would have been degrading for anyone," she told The Times in 1982. "I began to emotionally armor myself for what I knew I had to do, and how very lonely out there it was going to be."

Rubinstein told The Times in 1985 that she was looking for a way to get involved in the fight against AIDS when she was approached to play the mother in the campaign L.A. CARES (Los Angeles Cooperative AIDS Risk-Reduction Education Service), which was launched in early 1985.

The same day Rubinstein was asked to do the campaign, a friend of hers died of AIDS.

In television spots, Rubinstein played the mother pleading with an unseen son to "play safely." In videos made to be shown in gay bars, her sons appeared as bare-chested young men.

The campaign featuring Rubinstein's "mother" character also included a series of ads in newspapers and on billboards and buses.

In one ad with the words "Don't forget your rubbers" at the top, Rubinstein is seen wearing an apron and talking to her son, who is clad only in shorts and holding an umbrella. At the bottom, it says, "L.A. CARES . . . like a mother."

"She was one of the very first Hollywood celebrities to speak out on HIV and AIDS," said Craig E. Thompson, executive director of AIDS Project Los Angeles.

"It was the first AIDS education and prevention campaign in Los Angeles and one of the very first in the United States," added Thompson, who said calls to the organization's hotline "skyrocketed after the campaign came out."

Rubinstein had no immediate surviving family members.

No funeral service will be held, but a celebration of her life will be held at a later date.