HOLLYWOOD — In 2004, "The L Word" was hailed as a groundbreaking look at the sexed-up lives of lesbians in Los Angeles. Now in its fourth season, the Showtime series' cast has expanded to the point where its women seem to constitute a small city unto themselves.

Increasingly, the new additions are well-known actresses who have found themselves outside of the narrow range of options available. Kristanna Loken, the Nordic cyborg from "Terminator 3," plays a single mom. Cybill Shepherd joined the Sapphic ensemble in this season's second episode, playing the boss of Bette (Jennifer Beals — an "L Word" star since it began). And to heighten the nostalgic "I love the '80s" vibe evoked by the very idea of Shepherd and Beals acting together, Oscar-winner Marlee Matlin joins the cast as Bette's new love interest.

Twelve of "The L Word's" 13 regular cast members are women. That represents an unprecedented majority for a television series, particularly when you consider that other female-driven shows, such as "Desperate Housewives" and "Grey's Anatomy," usually require that each woman has a male counterpart.

And if "Desperate Housewives" was praised from its start for offering meaty parts to actresses, the "The L Word's" casting in Season 4 is an example of a series that keeps doing it — and adding them as flamboyantly sexual characters, to boot. (It's a strategy that is not without risks, if you ask Loken: Assembling all that grievously ignored female talent offers a unique creative opportunity, but also, it must be said, a certain built-in combustibility.)

In a telephone interview, Ilene Chaiken, the series' creator and executive producer, said, "We all know that there is an incredible dearth of roles of substance for actresses in every single age category." She continued: "It gets truer as women get older."

From the inception of "The L Word," Chaiken has taken advantage of Hollywood's penchant for ageism, and more broadly, the film and television world's static idea of who can play a romantic lead.

Showtime executives had told her that they expected her to cast only unknowns, and they were enthusiastic about the show despite that hurdle.

Chaiken recalled: "I said, 'That's great, I'm really delighted by your support for the show and the premise and really thrilled to know I can make it regardless of the actresses available. That said, I wager you that we're going to cast some stars.' "

Her confidence was borne out when Beals accepted the part of Bette, and Pam Grier was cast as her sister. Both actresses had experienced ups and downs after starring in iconic projects early in their careers: Beals as the leg-warmer-wearing welder/dancer of 1983's "Flashdance," Grier as the gun-wielding vigilante of "Foxy Brown" in 1974. The two had carved out a space for themselves in independent films, but being able to cast them as leads, Chaiken said, was "a great opportunity once we started putting the show together."