As far as it goes, the new campaign by the tobacco industry to discourage teenagers from smoking is certainly a welcome development.

But it doesn't go nearly far enough.Besides its recent decision to end the practice of giving free samples in public places where youngsters can get them, the tobacco industry also should stop aiming cigarette ads at young people and stop sponsoring youth-oriented activities like rock concerts and tennis matches.

To put this problem in perspective, keep in mind how much has been accomplished by the campaign to alert the public to the dangers of smoking - and how much remains to be done:

- In 1965, 40 percent of all adults in the United States were smokers. Today, fewer than 29 percent smoke.

- Nearly half of all living adults who ever smoked have quit.

- Between 1964 and 1985, about 750,000 smoking-related deaths were avoided or postponed.

It's no accident that these gains have been made since the requirement of health warning labels on tobacco packages and advertising - and since 400 communities have restricted smoking in public places. Remember these accomplishments the next time someone sneers at the suggestion of health warning labels for liquor bottles, calls for the legalization of marijuana or insists that the war on drugs cannot be won.

Despite the gains of the anti-smoking campaign, there are still more than 50 million smokers in America, smoking has declined less rapidly among women than among men, and children are experimenting with cigarettes at even younger ages.

The upshot is that smoking, which is responsible for at least one of every six deaths in the United States, is still the single most preventable cause of death.

The challenge, then, is to welcome the latest efforts to discourage teenagers from smoking but keep making even more demands on the tobacco industry.