Lawyers suing the tobacco industry gathered here today, swapping tips and legal strategies and assuring each other that their clients -- diseased and injured smokers and users of smokeless tobacco -- will triumph over the tobacco companies in court in a few years.

At least one plaintiff will prevail by mid-1988, John F. Banzhaf III, a pioneer anti-smoking crusader, told a session at the annual meeting of the Association of Trial Lawyers of America (ATLA).

Banzhaf is executive director of Action on Smoking and Health (ASH) and a George Washington University law professor.

Banzhaf and other speakers emphasized that the environment for lawsuits against the industry has improved drastically since the defeat of the first wave of smokers' litigation in the 1960s.

Improved medical knowledge, a series of court rulings, and a growing public perception of smoking as socially unacceptable will help the trial lawyers in their suits, Banzhaf said.

But there were notes of caution based on another perception: that the industry will fight desperately to defeat the second wave of litigation.

Even so, Northeastern University law professor Richard A. Daynard saw what he termed a "David and Goliath" situation. His Tobacco Products Liability Project sponsored the session to "get the Davids together," Daynard said.

One of the persons cheering the lawyers on rolled himself into the meeting room in a wheelchair. He is Harry Hall, a long-time heavy smoker who lost his legs to cardiovascular disease, part of his throat to cancer and a portion of his tongue.

He also has chronic obstructive lung disease, or emphysema and blames his health complaints on the results of smoking.

Hall's lawyer, former ATLA president J. D. Lee of Knoxville, said that Hall had volunteered to come. He asked his client about the first amputation: "Did you ever think for a minute that smoking would cause the loss of a leg?"

Hall, speaking with difficulty, and not always audibly, said that the possibility hadn't occurred to him. He also said that the cigarette package warnings had not forewarned him that the amputations and emphysema were in store for him.

Lee is set to try the first case in the second wave in Knoxville Sept. 23. His client in that case, Floyd Roysdon, smoked for 38 years, suffered cardiovascular disease and lost a leg.

In a sharp contrast, Melvin Belli, known as the "King of Torts," told of a case he plans to try in Santa Barbara. There, he said, "people like fresh air . . . like seaweed." Consequently he said, he will urge jurors drawn from the area to return a verdict for his client, "if you really want fresh air."

His case involves a 68-year-old man, John Galbraith, who smoked three packs a day and eventually died of cancer and emphysema.

Two leading thoracic surgeons from Boston, long-time smoking foes, denounced the industry, which was unrepresented at the session.

"You lawyers have before you the most noble of all purposes," said Dr. Dwight E. Harken.

He said the lawyers can "strike a lethal blow" at the most important single cause of preventible disease and death. Federal health authorities hold smoking responsible for an estimated 350,000 American deaths a year.

Harken also said that the public at large is increasingly unwilling to pay medical costs "for the other guy's damn foolishness . . . for people who would self-destruct."

Dr. Richard T. Overholt said, "This should be a joint humanitarian fight with a giant wicked industry."

Dr. Alan Blum, editor of the New York State Journal of Medicine, said that the cigarette makers "are child molesters -- they are aiming at children." He accused the mass media of being "willful colluders in the promotion of cigarettes to children."