Magnificent Obsession

Roger Ebert's a fan; so is Jerry Lewis. Rush's Geddy Lee watches it religiously on tour. Ginger Rogers uses it to catch all the movies she missed while she was making movies. It's the American Movie Classics channel — AMC to the helpless old-movie junkies who watch it until their eyes bleed-and in eight years of operation, it has become one of the most curious, beloved, and dangerous pit stops in the backwaters of multichannel choice.

Dangerous because this stuff is addictive: For the 40 million subscribers who either get it for free or (mostly in cities) pony up an additional fee, the Cablevision Systems- owned channel constitutes an around-the-clock revival house. Bona fide classics like King Kong snuggle next to irresistible obscurities such as Forty Naughty Girls, and they're all wrapped in a reverent bijou gestalt that can make the modern world seem far, far away. This is more than nostalgia, though; to viewers who get sucked in, AMC can be an enjoyable sickness. Here are six symptoms:

1. Most people keep channel hopping when they see black-and-white footage; you screech to a halt.
With five major film libraries and 3,000 titles to draw from, the AMC schedule is a movie freak's fantasy. True, Ted Turner's TBS and TNT have dibs on the MGM greats, but AMC fiends get to pig out on Universal horror classics like Bride of Frankenstein and The Mummy. The rarely shown Paramount library is here too, with its roster of directors like Ernst Lubitsch, Billy Wilder, and Mitchell Leisen. So is the deco brilliance of RKO, the corn-fed Americana of 20th Century Fox, and Sam Goldwyn's classy showmanship.

2. You find yourself discussing the merits of Betty Grable with total strangers.
For film director Tom Ropelewski (Madhouse) and his screenwriter wife, Leslie Dixon (Outrageous Fortune), AMC has become a kind of social scanning device. ''It's an intelligence test for people we meet,'' Dixon says. ''It used to be which books they read was the tip-off; now it's whether they're onto AMC.'' New York actor/writer David Toussaint, 28, has become an active proselytizer, not unlike those people you see at the airport.''I've gotten other people addicted, or have gotten them to watch my tapes,'' he says. ''I end up having long, random discussions at work.''

3. Your sleep and work habits suffer, and you don't care.
One Manhattan publishing VP prefers to remain anonymous in her dependency because she doesn't want her boss to know she's watching three Ray Milland movies a night instead of reading manuscripts. ''I was thinking the other night,'' she confesses, '''Why does it take four months to get through a book where I used to go through several a week?'''

4. You tape movies you will never pop back into your VCR.
Screenwriter Jeff Burkhart (Defenseless) is one of the many who have found their lust to time-shift to the past spiraling out of control. ''It got to the point where it became obsessional,'' he says. ''When you have 600 tapes, you realize that you can't watch them if your life depended on it.'' Burkhart now insists that he has gone successfully cold turkey.

5. Your respect for Bob Dorian acquires religious overtones.
Every month, AMC's silver-haired prime-time host cuts 35 to 40 ''intros and outros'' — on-air bits that meld history, trivia, and nostalgia. His is a class act (especially compared with the bow-tied daytime host, Gene Klavan, who comes off like the film nerd from hell), and it has made the 58-year-old theater actor and longtime film buff a new man. The viewer mail — some 450 letters per month, usually addressed to Dorian — is a testament to the emotional connection that AMC addicts feel with this keeper of the flame; Toussaint uses the words warm and fatherly to describe him. Recently, Dorian came out of a Richmond hotel to find that a small clutch of fans had been waiting since 5 a.m. to get his autograph. ''I wish people had done that when I was doing stage work,'' says Dorian, a little wistfully, ''but there it is.''

6. You hope they never find a cure.
Besides, you can stop whenever you want. It's a matter of willpower, that's all. Just one more Claudette Colbert.