Downey may be one of the lucky ones. His recent troubles have focused attention on the reemergence of heroin as Hollywood's It drug, the illegal substance of choice that's become for slacker-era stars what cocaine was for their counterparts in the late '70s and '80s. Not only has the Partnership for a Drug-Free America launched a new anti-heroin campaign, but even Republican presidential candidate Bob Dole has cannily pounced on the problem, denouncing the entertainment industry for ''glamorizing'' heroin in his Republican radio address July 27. Police say heroin's rise in popularity stems from an increase in the drug's purity in the last seven years, from about 4 percent to between 35 and 40 percent. As a result, users can smoke or snort it and avoid the stigma of shooting up. In fact, Partnership reports a 68 percent increase in heroin-related emergency room episodes from 1988 to 1994. Models are known to favor the drug, and fashionistas have been criticized for encouraging heroin chic, the wan, early-Marianne Faithfull look prevalent in magazine spreads. ''Heroin is hot,'' says Det. Frank Lyga, of the LAPD's Hollywood narcotics division. ''Downey is business as usual. River Phoenix and John Belushi didn't stop anyone. They're heroes now. Downey is just somebody who got caught.''

Downey is the first actor since Phoenix whose heroin problem has become public, but there are reports that a number of Gen-X stars, including at least two A-list actresses and two A-list actors, are struggling with heroin addiction. A former child star was reported to have gone to rehab for addiction to the drug last fall. Courtney Love, who has admitted to heroin use in the past, had to have a reported six-figure bond posted as a condition of getting the part of Althea Leasure in The People vs. Larry Flynt, the upcoming movie about Hustler publisher Larry Flynt. (To be fair, Love is said to have shown up, done her job, and caused no problems.)

While heroin is seen far less frequently in the TV industry, which one veteran comedy writer with a history of heroin abuse calls the ''squarest'' area of entertainment, the drug's impact on the music industry has been profound. Five young musicians — Jonathan Melvoin, who was touring with the Smashing Pumpkins, Bradley Nowell of Sublime, Dwayne Goettel of Skinny Puppy, Kristen Pfaff of Hole, and Stefanie Sargent of 7 Year Bitch — have all died from heroin-related causes since 1992. And although Blind Melon's Shannon Hoon died of a cocaine overdose last fall, he had recently been treated for a heroin habit.

Just since April, when Stone Temple Pilots canceled their summer tour and frontman Scott Weiland went into court-ordered rehab to try to kick his habit, several other rockers' struggles with the drug have surfaced. David Gahan of Depeche Mode was arrested for heroin possession on May 28; he is undergoing court-required treatment. And Philip Anselmo, the lead singer for Pantera, overdosed on heroin July 13 and now says he was dead for five minutes before being revived.