The 16th annual "Where We Are on TV" report released Wednesday by GLAAD found that 2.9 percent of actors appearing regularly on prime-time network drama and comedy series in the 2011-12 season will portray gay, lesbian or bisexual characters.
That's down from 3 percent in the 2009-10 season and 3.9 percent last season, when there were 23 out of a total of nearly 600 roles.
The 2008-09 season saw an increased representation of 2.6 percent.
Only five of the 19 gay and lesbian characters this season are nonwhite, GLAAD found.
Using information provided by ABC, CBS, Fox, NBC and CW, the group reviewed 91 scripted series announced to air this season.
Among broadcast series with gay and bisexual characters, GLAAD cited CBS' "The Good Wife," the CW's "Ringer" and NBC's "The Playboy Club." Comedies include ABC's "Modern Family" and Fox's "Glee."
Fox leads the networks in gay representation, with eight regular characters out of a total of 117.
The number of gay and bisexual characters on cable networks has also fallen slightly, from 35 last season to 29 in the upcoming season.
As it did last year, HBO has the greatest number of gay and bisexual characters, with 11 regular and recurring characters. Showtime is close behind with 10.
The HBO drama "True Blood" remains among the most inclusive series on television, featuring six characters, tied with the Showtime series "Shameless," the group found.
Some of TV's most popular shows "weave story lines about gay and lesbian characters into the fabric of the show," said GLAAD acting President Mike Thompson. "Americans expect to see the diversity of our country represented in their favorite programs, and that includes gay, lesbian, bisexual and transgender people."