The plight of America's homeless citizens is really no laughing matter - except once a year on HBO.

Comic Relief III, the pay cable service's annual fund-raiser for the homeless, will air for three consecutive hours this weekend beginning Saturday at 10 p.m. and continuing through 1 a.m. Sunday.And you don't even have to subscribe to HBO to see it. As has been the case in past years, HBO will unscramble its signal for the duration of the event. TCI, the largest local cable company, will also make "Comic Relief" available to all of their basic cable subscribers on a basic cable channel. (Hint: Check the channel that had HBO's free peek programming last weekend.)

A word of caution, however, to those who aren't used to the premium cable brand of comedy: Keep your zapper handy. While each of the previous two "Comic Relief" specials has featured some hilarious moments (most of them belonging to Robin Williams, who co-hosts the fund-raiser with Billy Crystal and Whoopi Goldberg), there have also been moments of extreme crudeness and vulgarity, and more than a few routines that were just plain dumb.

The same will certainly be true this year. With a scheduled cast that includes a mix of actors (Kirk Cameron, Cher, Charlton Heston, John Larroquette, Fred Savage and the entire cast of "Married . . . with Children") and comics (Louis Anderson, Elayne Boosler, Bob Goldthwait, Arsenio Hall, Richard Lewis, Howie Mandel, Joe Piscopo, Paul Reiser, Garry Shandling, Martin Short, Alan Thicke, Jim Varney and Steven Wright), "Comic Relief III" will have highlights - and lowlights. You'll be able to see the highlights in an hour-long taped special that HBO will air in a few weeks. The lowlights will hopefully soon be forgotten forever.

But if you don't have HBO you won't be able to wait for the condensed version. So if you feel you must tape it, keep a finger on the pause button. And make sure the kiddies are asleep. Sound asleep.

VIEWER DISCRETION is also advised for COPS, Fox's new reality-based series that airs Saturday at 8 p.m. on Ch. 13. In case you missed the series' sneak preview last week, this is a half-hour program that follows the personal and professional lives of police officers in Broward County, Fla. There is no script and there are no actors. It's just real-life law enforcement - as it happens.

For example, in the premiere we saw officers smashing through doors to make a drug bust, chasing bad guys and fishing a dead body out of a lagoon. OK, OK - so that sounds an awfully lot like what we'd see on "Miami Vice" any week. Obviously, they're not going to show us 22 minutes of police officers handing out traffic tickets and eating at greasy spoons. They're going to focus on the exciting stuff even though the show's producers promise we won't see a gun fired in the first 10 weeks.

Still, this has a gritty realism that is hard to resist. In a way it's kind of like driving by an accident on the freeway. It's hard not to crane your neck a little for a better view.

But you should know that you're taking a chance when you do so. You're probably not going to like everything you see on "COPS" (that bloated body coming up out of the water was a little hard to take). But you are going to see a program that is close enough to police reality that it has been endorsed by the American Federation of Police.

And unless I miss my guess, it will probably also be remembered as the show that started a trend toward similarly structured programs about real-life doctors, real-life lawyers - and maybe even real-life journalists.

- AND AS LONG AS we're talking about weekend television programming, you might as well start making your decision for the big viewership battle on Sunday night. While ABC is presenting part one of the two-part The Women of Brewster Place (8 p.m., Ch. 4) with a 67-pounds-heavier Oprah Winfrey, Jackee, Cicely Tyson, Robin Givens, Barbara Montgomery and Paul Winfield, NBC will counter with the network premiere of Return of the Jedi (7:30 p.m., Ch. 2). CBS, meanwhile, will be taking its 31st journey down the yellow brick road with The Wizard of Oz (7 p.m., Ch. 5), currently celebrating its 50th anniversary.

So what's it going to be - Oprah, Ewoks or Munchkins? Your answer probably depends on how big a fan you are of the two classic films. And while we'll talk more about "Brewster Place" in Sunday's TV Week, let's just say here that it's a good - not great, but good - story. The cast is excellent, and even though the NAACP is upset about the way black men are depicted, it's a compelling enough story to justify the time spent on it Sunday and Monday.

But if you're a "Star Wars" junkie, none of that matters, does it? You'll be watching Luke and Leia and Han and Darth Vader - even if you've already seen "Jedi" a dozen times. And if you're totally into "Oz," you'll be tuned to Ch. 5 to watch Dorothy and the Tin Woodsman and the Scarecrow and the Cowardly Lion.

And Toto, too.

- THE EDDINGS FAMILY of Bountiful writes: "We would like to praise Ch. 14 for showing "Ring of Bright Water," a story to uplift and entertain. It combined a number of artistic and human areas. Besides the beautiful scenery and hilarious situations, it showed us the good and wonderful feelings of loving a pet. Young people who watched the movie could contemplate love and caring between a man and a woman without crudeness. It is a relief not to have to hold your breath for the next embarrassing scene. We hope Ch. 14 will look for more of these movies which we all can watch."