Aspiring funnymen and women mustn't miss this weekend's first-ever Philadelphia Improv Festival. That's two days of off-the-cuff comedy provided by some of America's best improvisers. There are no guaranteed gags, no recycled yarns and no cow too sacred to butcher in the name of that "I need a joke and I need it now" sweaty-palms panic.

The festival lineup features more than 100 comedians and 24 acts, including local favorites The N Crowd, ComedySportz, Rare Bird Show and 13 Skirts. Out-of-town headliners include Chicago's Upright Citizens Brigade Touring Co. (UCB), New York's Ms. Jackson and North Carolina's Beatbox.

Festival highlight UCB first made a name for itself through its eponymous cult TV hit; extensive touring, stints on Saturday Night Live and the opening of namesake theaters in New York and Los Angeles have since bolstered its reputation as a leading troupe in the development of zany and artful adult-edged comedy.

UCB New York artistic director and cast member Anthony King is a big fan of Philadelphia's comedy scene. "The audiences are really receptive, but they're also discerning and know what they like and what makes them laugh," says King, who's been working the local circuit for years. King says the two cities share a deep-rooted kinship and often trade acts back and forth. He also thanks UCB for introducing long-form improvisation to the Big Apple.

"Improv has grown on a national level, and as a result, our local scene has responded to this phenomenon," says festival organizer and Village Idiutz member Michael McFarland. The Idiutz organization, which launched PhillyImprov.com in an effort to unify the city's many troupes, now counts among its ranks top-shelf performers John Sales, Rick Horner, Alexis Simpson, Nathan Edmondson and Matt Nelson. "This serves as a networking tool to bring together the improv community at large and creates an atmosphere of cooperation, education, creativity and collaboration," Horner says.

So what happens when the audience doesn't find that mop handle/Virgin Mary joke as funny as you do? "While there may be a bad scene from time to time, our goal is always to support our scene partners and the ideas we're playing with," says King. "If something does start to go off the rails, we're not relying on tried and true gags. We're relying on the idea that as a group, we will never fail because we always have each other's back."

Philadelphia Improv Festival, Fri., Nov. 4, 6 p.m.-midnight.; Sat., Nov. 5, 5:30 p.m.-midnight, $15-$25 or $50 (two-day pass), 2111 Sansom St., www.phillyimprov.com.