On a recent episode of the UPN comedy "Half and Half," a male character has a one-night stand with an acquaintance. When it turns out the woman may be pregnant, his friends ask if he was "using protection."

"Not unless you mean deodorant," he says.

One friend berates him, saying, "I can't believe you had sex without a condom!"

Another chimes in, "How could you not put a jacket on your butler?"

That a UPN sitcom would revolve around sex isn't news. What is news is that "Half and Half" has joined a growing number of TV shows in warning its youthful audiences that sex is not as carefree as it often appears in the media.

Popular entertainment may be racier than ever, but many in the industry have been shaken by the spread of AIDS. Now they're looking for creative ways to put messages of responsibility in between booty calls.

Viacom, one of the world's biggest media companies, has embarked on a yearlong campaign to raise awareness about HIV and AIDS. This includes asking producers on Viacom-owned TV shows like "Half and Half" to work safe-sex messages into their scripts.

A recently released survey of more than 1,100 TV programs confirms that television is far more likely to include positive messages about "safe sex" and even abstinence than it was a few years ago.

Even more encouraging to youth-health advocates: TV shows aimed at teen-agers are more likely than most shows to mention the risks and responsibilities of sexual activity.

Victoria Rideout of the Kaiser Family Foundation, which conducted the biannual study, credits teen-oriented shows like "90210" and "Dawson's Creek" with showing how safe-sex messages can be artfully written into scripts.

"When somebody takes the high road and succeeds," Rideout said, "others in the community learn from that."

Still, most mentions of sex on TV continue to be made without any regard to consequences. And hot new reality shows like "Blind Date" and "Joe Millionaire" have unscripted dialogue, raising questions about whether the sexual shenanigans on those programs will ever carry warning labels.

The Kaiser Foundation study found that among the 20 shows most watched by teen-agers last season, 83 percent contained some form of sexual content, whether spoken or depicted. And while most programs showed small acts of intimacy such as kissing, 14 percent of teen-oriented programs mentioned or depicted sexual intercourse - a figure that's doubled in the last four years.

In those scenes, however, someone mentioned the risks or responsibilities of sex - what the Kaiser researchers call "safer-sex references" - nearly half the time. Among all the shows from the 2001-02 season in the Kaiser report, 26 percent were found to have safer-sex references in them. That figure also has doubled since the 1997-98 season.

Rideout called the results positive, though she admitted TV still sends mixed messages to kids.

"There's a lot of 'non-safer' sex in a show like 'Friends,' but the condom episodes they did, I thought, were quite funny," Rideout said.

Sex educators who teach kids about sexuality weren't so amused.

"I'm surprised to hear the percentages are so high," said Tracey Allen, a community educator with Planned Parenthood of Kansas and Mid-Missouri. Allen gives sexuality talks to about 5,000 teens every year, and when the subject of sex on TV comes up, she said her students don't bring up the cautionary messages.

"Usually they just say that (the characters) are having sex," Allen said.

TV's newfound caution about sex is welcome news to those who teach Missouri's controversial abstinence-only curriculum. Fifty percent of teen-agers are sexually active, but that means that 50 percent of teen-agers aren't, noted Kathleen Welton, who coordinates abstinence programs at 12 schools in Missouri.

When TV shows warn about catching sexually transmitted diseases, or STDs, they have an effect, Welton said, because "kids consider STDs more of a deterrent than pregnancy." A teen-age boy in one of her focus groups put the matter bluntly: "STDs can kill you now," he said.

Such a deadly serious message might seem out of place in situation comedies, which dominate the list of shows most popular with younger audiences. In the 1980s it was common for sitcoms to take on "social issues." These "very special episodes" were later lampooned for their simplistic storylines and preachiness.

But now that the "social issue" is AIDS, a deadly disease that spreads through ignorance, many in the TV world feel that they really can make a difference.

"People seem to think that AIDS is under control and no longer a problem. They are, of course, wrong," said Dave Hackel, creator and executive producer of the hit CBS comedy "Becker." Like "Half and Half," "Becker" is a Viacom-owned program, through its Paramount division.

So when Paramount approached Hackel about including AIDS awareness in a "Becker" episode, "we were happy to do so," he said. Since the show's lead character, John Becker, is a doctor, the show's staff already had a team of medical sources they could consult on the script.

In the episode, which aired Feb. 2, Becker (played by Ted Danson) has a 15-year-old patient who brags about being sexually active without protection. "Becker threw a bit of a scare into him and, in doing so, got the message across to the teen and, hopefully, to our viewers," Hackel said.

But what about programs that don't have writers or scripts? Two of the most widely viewed TV shows last month among teen-agers were "Joe Millionaire" and "The Bachelorette." On a recent episode of "Joe," a man and woman snuck off into the woods at night for a sexual encounter. The scene was too dark to see anything, but microphones picked up the rustling of clothes - and some other sounds. When those noises were described with subtitles, very little was left to the imagination.

Even more prurient fare may be on the way. The trade publication Electronic Media printed a report of one show idea currently making the rounds: "Who Will Father My Baby?" in which young men "vie to accommodate a young woman looking to become pregnant."

Because reality shows don't rely on preordained storylines, a reference to safe sex can't just be written in. A Viacom spokesman said reality shows weren't included in the company's AIDS-awareness initiative, though public service announcements might air during commercial breaks of Viacom reality shows such as "Survivor" and "The Real World."

But sex educators say that no matter what is shown on TV, the most important thing is that parents watch at least some of their kids' favorite shows and talk about them.

One third of teens reported having a conversation with their parents about sex based on something they'd seen in the media, the Kaiser Foundation's Rideout said.

"So it can be an easy way in for parents to talk about something that's difficult to bring up, whether you agree with what you saw on TV or not," Rideout added.