Here's one thing you won't be seeing much of when the big TV networks roll out their new sitcoms and drama series this fall: black people.

In what is likely to be the whitest television season in a generation, not one of the 26 new shows set to debut on ABC, CBS, NBC and Fox will star an African American. Blacks, along with Hispanics and Asian Americans, will occupy few secondary roles as well.

The new season continues what amounts to a disappearing act for blacks and black-themed shows during the 1990s. After a decade in which Bill Cosby ruled television, and predominantly black sitcoms like "A Different World" and "The Fresh Prince of Bel-Air" broke through to general audiences, African Americans are accounting for a steadily declining share of roles as broadcasters chase more numerous and affluent white viewers.

Last season, for example, only four shows with blacks or other minority actors in lead roles survived a full season. Three of these were on CBS, and two featured Cosby ("Cosby" and "Kids Say the Darndest Things"), while ABC had the family sitcom "The Hughleys." At mid-season, Fox offered "The PJs," an animated sitcom featuring African American Claymation characters. Among the big four, NBC -- whose hit sitcoms "Seinfeld" and "Friends" have portrayed a Manhattan largely devoid of minorities -- didn't carry a single show with an African American in the lead.

The trends have alarmed the nation's largest civil rights organization, the National Association for the Advancement of Colored People. At the NAACP's national convention in New York yesterday, President Kweisi Mfume blasted the ebbing diversity and suggested that legal action could be warranted.

"When the TV viewing public sits down to watch new prime-time shows scheduled for this fall's lineup, they will see a virtual whitewash in programming," Mfume said in an address to the group. "This glaring omission is an outrage and a shameful display by network executives, who are either clueless, careless or both."

Mfume, who called for federal hearings on station and network ownership, said the NAACP plans to monitor the movie and TV industry out of its new branch in Hollywood. He said the NAACP is "actively exploring" litigation against the four networks and boycotts of their sponsors, though he wasn't specific.

The top programming executives of CBS, NBC and the smaller WB and UPN networks acknowledged the general racial trend in interviews, but each defended his network's fare (Fox's top executive, Doug Herzog, and ABC Entertainment President Jamie Tarses were not available for comment, despite repeated requests during the past month).

"Most networks and production companies are aware of the need to strive to diversify," said Leslie Moonves, president of CBS, the network most popular among both black and white viewers last season. "It's important for us to represent America the way it really is."

But Moonves called the absence of blacks in major roles on forthcoming shows "an exception." He believes the pendulum will eventually swing back. "Everything on TV is cyclical," he said.

Yet the trend seems to have largely gone in one direction for several years. During the 1993-94 season, according to the Washington-based Center for Media and Public Affairs, 18 percent of the characters on entertainment programs were African American. In the season just completed, the figure had fallen to 10 percent.

Since African Americans actually make up almost 12 percent of the U.S. population, that means the leading networks now underrepresent them on the airwaves. Hispanic Americans have had a similar fate for years. Although Latino characters increased from 2 percent of all roles in 1992-93 to 3.8 percent last season, this still is far less than the 11 percent share of the U.S. population that identifies itself as part of the fast-growing Hispanic segment.

The trend for blacks is actually worse than the percentages indicate, said Robert Lichter, the center's director. He pointed out that since all four networks now pack their schedules with newsmagazine programs like "Dateline" or "60 Minutes," there are fewer dramas and sitcoms on their schedules. In effect, that means blacks are accounting for a smaller share of a shrunken pool.

This pattern runs counter to statements made recently by some of the networks' top decision-makers. Tarses, ABC's entertainment president, told reporters last summer, "I think all the networks are working on" increasing roles for blacks, as well as other minorities. "I think we're always looking to make the ensembles of our shows as eclectic as we can."

In an interview, NBC's chief entertainment executive, Scott Sassa, repeated his determination to provide "more diversity, less sex, less New York and more family" in his network's shows. "It's about variety," he said. "One point is diversity. We made a mistake having too many things that are unoriginal and alike."

Black characters do have prominent though usually supporting roles in several network dramas, including "NYPD Blue" and "The Practice" on ABC, "Ally McBeal" on Fox, "ER" and the canceled "Homicide: Life on the Street" on NBC, and "Touched by an Angel" on CBS.

In a noteworthy exception, CBS has scheduled producer Steven Bochco's "City of Angels" -- a new medical-center drama featuring a mostly black cast -- as a mid-season replacement next year. The program will be among the few dramas in TV history in which black characters predominate.

But network sitcoms are almost exclusively white -- a reversal from the days when "crossover" shows like "Sanford and Son," "Good Times," "The Jeffersons," "Amen," "227," "Diff'rent Strokes," "Family Matters" and "Fresh Prince" dotted network schedules. Indeed, Fox built its challenge to CBS, ABC and NBC by attracting the young -- and often black -- audience overlooked by the networks with "black" comedies like "Martin," "Roc," "Living Single" and "In Living Color."

Filling some of the void left by the big four are the WB and UPN networks, which started four years ago. Both air a number of shows starring African Americans, featuring comedian Jamie Foxx, in a self-titled sitcom, and pop singer Brandy ("Moesha").

Jamie Kellner, WB's chief executive, said his network "from the beginning looked at viewer groups that were not well represented on network TV. Young people were not well represented. African Americans were not well represented. . . . If the other networks don't want to put those shows on, it makes good business sense for us to pursue them."

But the WB and UPN are still small, with original programming airing only five nights a week last season and together attracting only about 8 percent of the TV audience each night during prime-time hours. ABC, CBS, NBC and Fox, meanwhile, collectively attract more than half of all viewers each night.

What's more, both WB and UPN cluster their "black" sitcoms on their schedules, lending the impression that these shows are segregated from the rest of the lineup.

Some blacks are suspicious about whether the start-up networks are really committed to black audiences. At a recent industry dinner in Los Angeles, comedian Steve Harvey, who stars in a self-named WB sitcom, voiced his doubts publicly, noting that Fox has abandoned its African American stars for the likes of "Manchester Prep," one of several new all-white shows about the lives and loves of young people.

Black actors and producers also complain that series with a strong appeal to black audiences are the last to be added and the first to be dropped when ratings fail to meet expectations.

This perception was reinforced recently when Fox moved "The PJs" off next fall's schedule and replaced it with a half-hour version of "Ally McBeal." The move angered "PJs" executive producer Eddie Murphy, who is also the voice of one of the characters. Fox says the sitcom will be brought back at mid-season.

"The pendulum may swing back, but it never seems to swing back too far in our direction," said James McDaniel, the African American actor who portrays Lt. Arthur Fancy on "NYPD Blue." "To be told, `You're not in vogue for the moment' makes [one] feel like a second-class citizen." A proposed program featuring blacks, he said, "just in its very nature is perceived to be much less valuable than a comparable white project. That's just a fact."

Said Tim Reid, a veteran actor and program creator ("Snoops," "Frank's Place" and the pay-cable series "Linc's"): "Hollywood is supposed to be a liberal bastion, but in reality, it's `Do as I say, not as I do.' This is the last segregated industry in America."

Both McDaniel and Reid suggest the problem stems from a lack of diversity in the networks' executive suites. Although women have recently ascended to the top programming ranks at the networks, no racial minority has ever overseen programming at a major network until Sassa, a Japanese American, was promoted at NBC last year. "In many cases," said McDaniel, "we're talking about [executives] who only know the mean streets of Malibu."

But the programming patterns have an economic root as well.

Network executives point out that black viewers form a relatively small part of the overall audience -- slightly more than one in nine -- and that white households are generally more affluent, which makes them more attractive to advertisers. In addition, blacks don't watch TV as a unified group and a "black" show is likely to appeal only to some black viewers. Young black and white viewers, for example, are more likely to watch the same program than are young blacks and older blacks. That means a "black" show is presumed to start off with a very small audience.

Moreover, the business of network television is evolving; the networks have moved away from serving broad, diverse audiences -- being all things to all viewers -- and instead are focusing on narrower demographic groups. With viewing alternatives proliferating and network profits declining, broadcasters want to attract the audience that advertisers covet most -- young, upscale viewers aged 18 to 49, or even 18 to 34.

In this calculus, appealing specifically to black audiences is relatively less important, some TV executives privately acknowledge. Said one: "The hard part is that cable [networks] can do a better job of specifically serving a minority marketplace. They don't have to appeal to as many people as we do."

Network programmers and advertisers have long known that blacks watch far more TV than whites -- about 40 percent more throughout the day, and about 9 percent more from 8 to 11 p.m., according to TN Media, an advertising agency. This means that advertisers already reach black viewers, reducing the incentive of the networks to create shows specifically for them.

"I'm not trying to accuse the networks of a conspiracy against blacks and Latinos; they're trying to reach the most people, and the most affluent people, possible," said Doug Alligood, who tracks black and white viewing habits for the ad agency BBDO.

But, he added, "I'm not saying they're right, either. It's really unfortunate that they can't reflect this country better. Blacks and Latinos are not poor and uneducated anymore. They show no sensitivity to the fact that we exist."

Staff writer Michael A. Fletcher contributed to this report.

CAPTION: When "Cosby" was the top-rated show, actors of color accounted for a significant percentage of lead roles on TV. Now, in the "Friends" era, the main color is white.