Portia de Rossi, left, and Ellen DeGeneres at a party in Los Angeles.

THE NEW YORK TIMES / AXEL KOESTER

There’s a bisexual woman in Bones and a lesbian couple on The Goode Family.

Dirty Sexy Money features a transsexual and Brothers & Sisters a gay marriage.

In Mad Men, the Emmy-winning drama set in the early ’60s, there’s Salvatore Romano, a self-loathing homosexual who marries a woman but pines for a male co-worker.

Never before have gay story lines been so prominent. Nor have there ever been so many gay, lesbian, bisexual and transgender characters on television — 83 by a recent count from the Gay and Lesbian Alliance Against Defamation, not counting reality shows, daytime dramas or gay-oriented cable networks.

Hollywood, with its depictions of cowboy lovers and lesbian neighbors, has done much to make gay men and women part of mainstream American life.

At the same time, gay actors like Neil Patrick Harris and T.R. Knight play heterosexual characters on TV and in film, while couples — Ellen DeGeneres and Portia de Rossi — are covered by celebrity magazines as if they were any old romance.

“We’ve gone from the revolution to the evolution,” said Howard Bragman, a longtime Hollywood publicist who is gay and has advised actors like Amanda Bearse, of Married . . . With Children and Dick Sargent of Bewitched on how to handle their coming out.

Yet for most gay actors, Hollywood is not a warm and fuzzy episode of Will & Grace. Today, it is certainly more acceptable to be openly gay. But these actors must still answer wrenching questions: Just how candid do you want to be? Would you be happy appearing only in comedies, or being pigeonholed as a character actor? And what does the line “You’re just not right for the role” really mean?

Jasika Nicole, 28, an FBI agent on Fringe, a new Fox drama, said that as bigger parts became available, her manager, John Essay, sat her down and asked how public she wanted to be about being a lesbian. Some roles could be lost, he told her, as would some fans.

Essay, who is gay, said he encouraged openness but warned clients of the risks.

“If it becomes exaggerated,” he said, “you just become the gay actress instead of a wonderful actress.”

Perhaps, he suggested, she didn’t want to be too vocal about it.

Nicole, who has a girlfriend, said she would just be herself. She has been open about her sexual orientation since she started dating women about 3 1/2 years ago, while she was filming Take the Lead with Antonio Banderas in Toronto.

Now, as she becomes better known, “There’s no way I can keep quiet,” she said. “I want to be clear this is my partner. I don’t want to make that shameful in any kind of way.”

But most other actors calibrate just how out they want to be. Openly gay can still mean they would rather not talk about it. Most gay actors are mum in public or on the set, even if they don’t hide their orientation in private, actors and others in the entertainment industry said. Although most may no longer participate in charades — the “girlfriend” on the red carpet, for instance — many adopt a don’t ask, don’t tell policy.

Why? For both men and women, being openly gay, at least for now, means giving up any hope of superstardom.

“The industry is persuaded that being known as gay will undermine your credibility both as romantic lead or an action star,” said Larry Gross, director of the Annenberg School for Communication at the University of Southern California and author of a book on media portrayals of gays and lesbians.

“They don’t test it,” he said. “We’re waiting for the Jackie Robinson moment when someone tests that assumption and discovers it’s not true.”

Gay actors don’t just lose the potential of becoming the next Brad Pitt or Reese Witherspoon, they lose the opportunities for fame that ensure plum jobs, said Jason Stuart, an actor and comedian who chairs the lesbian, gay, bisexual and transgender committee of the Screen Actors Guild. It is no coincidence, he said, that even the title role in Milk, based on the slain gay hero, Harvey Milk, went to Sean Penn, an Oscar-winning actor who is straight.

“There are not enough famous gay actors to play these roles,” he said.

But some casting directors said it was now much easier to cast gays. Mary Jo Slater, a film and television casting director, said barriers were falling because of the success of shows with openly gay actors in them.

Slater cast a transgender actress, Candis Cayne, in Dirty Sexy Money, and noted: “She’s, like, a big star now.”

“I look at their ability to perform the part,” she said. “I don’t really think it matters.”

But what about straight parts? Chad Allen, 34, a child actor on shows like St. Elsewhere and Dr. Quinn, Medicine Woman, said steady work dried up in 1996 after a tabloid ran a photograph showing him kissing another man. The Dr. Quinn cast was supportive, and he remained in the family-oriented show, he said, but after the series ended, “It was tough.”

“I couldn’t get an audition for a pilot after that,” he said.

But Allen, who attended college and continued to do some work in film, found new roles a few years ago, with the advent of gay-oriented cable networks. In channels like Here! and Viacom’s Logo, openly gay actors have played lead roles as private detectives, vampires and superheroes. Allen stars in a mystery series on Here!, in a role he describes as “a good detective who happens to be gay.”

And in a sign of the times, the show gave him opportunities for gay and heterosexual guest roles in television shows like CSI: Miami and Cold Case.

In 2006, Allen incurred the wrath of some conservative ministers after he was cast as the lead in End of the Spear, produced by an evangelical film company, about five American missionaries killed in 1956 by an indigenous tribe in Ecuador.

The church pastors objected to his sexual orientation and his political advocacy for gay causes, but Allen said the fear of casting someone like him is less and less an issue. “We’ve been witnessing a slow erosion of this fear as audiences show up,” he said.