"It's definitely very exciting," says Gant, who plays HIV-positive English professor Ben Bruckner in the Showtime drama, now in its fourth season on Sunday nights. "This show is unique in that it isn't just entertainment -- although it certainly is entertaining -- but it reflects these incredible social changes going on, as well as kind of being a catalyst for some of those changes."

"I think a lot of us took this job for that very reason," echoes Sparks, who plays Ben's life partner, Michael Novotny. "I know I did. When this show was first starting, both straight and gay actors refused to read for parts because it was considered career suicide. My manager said, 'This will either be an important, impactful show, or it will disappear. There will be no middle ground.' I took a chance that it would be socially relevant, and that's certainly how it has turned out."

When the series, adapted from a controversial but critically acclaimed 1999 UK miniseries, premiered in 2000, it was denounced in some quarters of the gay community for the casual sex and drug use among many of its characters, who frequented the gay bar Babylon. As those characters have aged and matured over the seasons, however, the show has likewise morphed into a more complex drama exploring both topical issues as well as the internal emotional lives of its characters.

This season, Ben and Michael prepare to adopt Hunter (Harris Allan), a troubled street hustler they took into their home last season. Their flamboyant friend Emmett (Peter Paige) tries to immerse himself in his new party planning business to get over his ill-fated affair with Ted (Scott Lowell), a crystal meth addict struggling to maintain his sobriety and re-establish connections with the friends he had alienated during a near-lethal bender.

Somewhat redeemed by his heroic acts of sacrifice last season, self-absorbed advertising genius Brian (Gale Harold) starts up his own public relations firm while fretting that his young boyfriend, Justin (Randy Harrison), is getting a little too drawn into a new gay vigilante group, the Pink Posse.

The sexual candor and outrageous, often blue, jokes are still very much a part of the show, but they are balanced by a slightly more reflective tone and compelling story lines that include the death of a series regular within the first few episodes of the season.

"This has always been the story of boys becoming men - not to exclude the women on the show," says Ron Cowen, who created the U.S. series with longtime writing-producing partner Daniel Lipman.

"It's about growing up, and the characters were in their mid to late 20s in the first two seasons, whereas now most of them are in their 30s. Before, they went out a lot. Now they are concentrating on family, relationships and careers. Many fans, I think, became more involved as the focus of these characters changed and became more complicated."

Cowen and Lipman both concede that they were startled by the storm of controversy that greeted the show upon its premiere.

"The response from certain elements of the gay community and press shocked us, actually," Lipman says. "If someone like our Brian character were straight, he would be considered a stud. Because he's gay, suddenly he's a slut."

"Many gay people seemed threatened by our decision to ... show gay characters who have a sex life," Cowen recalls. "Gay characters are usually clowns or eunuchs. That's a very prejudicial view. I'm not sure why so many gay people have this problem with seeing gay characters sexualized, but I can tell you, we're going to keep doing it."

Gant says he likewise was taken aback by the overt hostility some gay viewers expressed toward the series.

"I can certainly accept criticism about our show," he says, "but please, why not make it constructive criticism? We haven't learned to do that as a community. We devour our young. This show is an imperfect entity that is trying to serve and to tell our story in some way, at least a piece of it, and many in our community aren't willing to give that a chance. That's starting to change, I think, because all of us are growing up, and in that way what is happening on the show again parallels what is happening in our community."

Both he and Sparks agree with the many fans who feel the show really found its feet creatively during last season.

"Prior to this, there was absolutely nothing of this kind on American TV, nothing to talk about the lives and struggles of gay people, so viewers wanted the show to be all things to all people, which clearly was not possible," Gant says. "This poor show had so much on its back. Like Atlas, it was having to carry the whole gay world.

"The second season was all over the place, trying to find a way to honestly address what was going on for lesbian and gay people. Last season we totally just clicked into gear. We found these characters' voices and where they were going. Different people relate to different characters, but I have gotten some amazing e-mails from people saying that Ben just really resonates for them."

"Early on, I think Ron and Dan were throwing everything up against the wall to see what might stick and each episode had to wrap up at the end like a cartoon," Sparks recalls. "The third season, we got picked up for two seasons at once, so that gave them a chance to take a deep breath and plot their stories over longer time, so the stories had greater depth."

If some of the characters are mellower now, don't expect the series itself to turn a blind eye to controversy. Among this season's topics is a look at "bug chasers," gay men who seek out HIV-positive partners to infect them.

"We've always called the show a celebration of gay life," Lipman says, "and that has included both celebrating and going into dark places. We can't turn away from drug abuse and bug-chasing. It happens."