Thursday night, "The Sarah Silverman Program" debuted on Comedy Central. If it had aired on regular broadcast TV many punch lines and entire story lines would probably have been "bleeped" or cut. The comedian who has been called a "delightful potty mouth" certainly has a devoted fan base who has followed her from stand-up to the silver screen and now, to the home screen.

Cable television has long pioneered new frontiers in what's funny, allowing comedians to tackle taboo subjects with reckless abandon. That is, if they were male. The fact that Ms. Sliverman – considered one of comedy's rising stars with her engaging smile and bawdy humor – has been given room to run proves just how far women have come on the stand-up stage.

Yet, for every step forward, say many comics and cultural observers, when it comes to being funny, women still face many societal prejudices. Nice girls just don't act like that, says comedy veteran Rusty Warren, who recalls male audience members storming out of her shows. Not much has changed today, say observers who suggest that many people, men and women, find attractive, aggressively funny women like Silverman threatening.

Witness the recent column in Vanity Fair which declared "Women Aren't Funny" (written by Christopher Hitchens). And despite the fact that his ABC comedy employed numerous funny women, comic Drew Carey says the prejudices are real. It's not so much that women aren't funny, he explains, as that men don't want them to be funny. "Comedy is about aggression and confrontation and power," says the stand-up comic. "As a culture we just don't allow women to do all that stuff."

Certain roles have been acceptable for women since the rise of mass media: the sexy vamp (think Mae West) or the ditzy klutz (everyone from Carole Lombard to Lucille Ball and Debra Messing). "These roles aren't threatening to men," says actress Jennifer Coolidge who has made a career of crafting cunning but klutzy airheaded females. She adds, "they play into men's stereotypes of women as sexpots or stupid." Indeed, a pregnant Joan Rivers once worried if such a protruding reference to her sexuality, her belly, might hurt her career.

Comedy definitely mirrors the culture, says comedian Kelley Lynn, who is also an adjunct professor and teaches a comedy class at Adelphi University, in Garden City, N.Y. She says she is amazed at the differences between her male and female students. "The boys just seem to come in with all this confidence, whether their material is funny or not," says Ms. Lynn, "whereas the girls come in and say, 'Is this funny?' " Almost always, she adds, the material is just as funny, if not more so, but the girls lack the confidence to deliver it with conviction. "There will continue to be progress for women in the world of comedy as the world changes," Lynn says, "but it may take generations."

The rise of sketch comedy has helped women comics. The collaborative form entered mainstream culture in the '70s with groups such as Monty Python and TV shows such as "Saturday Night Live" (SNL), which has since turned it into a household term. The form has helped nurture generations of successful women comics such as Jane Curtin and Tina Fey. (Fey now has her own show on NBC, "30 Rock," based loosely on her experiences at SNL.)

"We've been incredibly friendly to women over the years," says SNL executive producer Lorne Michaels, who has shepherded the show from its inception.

Sketch comedy is well-suited to encourage women, says Cherie Kerr, one of the founders of the seminal comedy troupe from the '70s, The Groundlings. "Suddenly, comedy wasn't so much about the solo stand-up anymore," she says. "It was about a whole group onstage, working together to make the skit work." While she says with a laugh that SNL is certainly a competitive place, the cooperation and working together is much more a woman's style than the confrontational style of stand-up comedy.

Silverman represents a generation of young comics who've come of age in an era of few restrictions. "I don't think anything is off limits, if it's funny enough," says Silverman. "If it's more funny than offensive to us, then it's fine, no matter what it is."

Nonetheless, says comic Paul Rodriguez, Silverman still faces yet another stubborn stereotype: Pretty women aren't funny, especially when spouting vulgarities. Men still put women on a pedestal where they expect them to behave, well, nicely – like a mother, says Mr. Rodriguez. "If an unattractive woman tells jokes, it's OK, we'll cut her a break," he says. "It's just a man's world, comedy is full of prejudices, whether we like it or not, it's true."

But good comedy is based on truthful observation, even if it's the painful reality that not much has changed when it comes right down to it, says Diane Salvatore, editor in chief of the Ladies' Home Journal. "People still tend to think of comedy as a job for men, sort of like the presidency," she adds with a rueful laugh.

For the past three years, the magazine has run an annual spotlight on "Funny Ladies We Love." The next one runs in March. Just like politics, good comedy takes courage, says Ms. Salvatore. "We want to do our part to support that."