In the fall of 1975, 55-year-old Ira H. Dishner, a "basically healthy man," according to his doctor, complained about sharp pains in his back and chest.

A month later, in November, his doctor's tentative diagnosis was verified: Dishner had mesothelioma, a rare cancer of the tissue surrounding the lungs. Chemical therapy slowed the fast-spreading cancer for a while, but on Dec. 16 of last year, Dishner died.

In a $3 million suit filed against Johns-Manville Corp., Dishner's estate claims the cancer was caused by asbestos manufactured by the firm and used at the Amoco refinery in Yorktown where Dishner had worked for 18 years.

The Dishner estate's attorney, Gene Locks, told the trial jury in U.S. District Judge Richard B. Kellam's court: "Asbestos killed him as surely as if he had been shot with a gun. The only difference is that it took longer."

The trial, now in its second week here, is being watched closely because it is the first of 40 cases involving more than 100 Virginians suing various asbestos producers and suppliers for more than $300 million.

Many of the plaintiffs are present or former workers at the Norfolk Naval Shipyard in nearby Portsmouth. Various studies going back to 1968 have identified shipyards - where asbestos is used extensively as insulation - as prime locations of asbestos-related disease.

But the plaintiffs' contention is the same in all the cases: Asbestos firms did not warn them - soon enough or adequately - about the hazards of asbestos. Many of the workers, now in their 50s, went to work at the shipyard in the 1940s during World War II.

Their stories, told in the legal language of depositions and in various medical reports, are filed in a third-floor office at the courthouse that is called the "asbestos room."

According to various accounts, the workers had only a dim awareness, if they had any at all, of what asbestos dust - made up of microscopically tiny, needle-shaped fibers that never decompose - could do to their bodies.

In the deposition he gave shortly before he died, Dishner said the only writing on asbestos packages he could recall was "the name John-Manville."

The plaintiffs contend that asbestos markers and suppliers not only failed to warn them, but actually concealed the extent of the hazards.

Dishner's lawyer, Locks, tried unsuccessfully to introduce minutes of various meetings of the Asbestos Textile Institute (of which Johns-Manville was a member). According to the minutes of the meeting, in March 1956, Dr. Kenneth Smith, medical director of the firm, "recommended very strongly" that the textile institute commission a study of the relationship of lung cancer to asbestos.

The institute, by a 6-to-2 vote, rejected such a study. "There is a feeling among certain members that such an investigation would stir up a hornet's nest and put the whole industry under suspicion," the minutes said.

But there is another side - the asbestos makers' - and that too is found in folders in the asbestos room.

For example, John-Manville supplied reproduction of all the warning labels it has used on its asbestos products since 1964.

There is the conclusion of a 1974 study commissioned by the Amoco refinery where Dishner was employed: "Workers who are required to work with asbestos-containing insulation are not likely to be exposed to concentrations of asbestos fibers in excess of the ceiling limit . . ."

As for the 1950s or earlier, when many of the plaintiffs began their exposure to asbestos dust, the companies argue that "the state of the art" did not indicate any more precautions than were taken. They contend that it was not until the mid-to late-1960s - after Dr. Irving J. Selikoff of Mount Sinai Hospital in New York published extensive documentation of asbestos as an occupational hazard - that they had evidence to justify more stringent precautions.

One of the nagging question - whether the companies' warnings were adequate - was dramatized during testimony at the Dishner trial last week. Frank Davenport, who works for a construction firm at the Amoco refinery, was asked by one of Dishner's lawyers, Robert R. Hatten: "Have you ever seen a warning or caution label on packaging?" "No," Davenport said.

Johns-Manville lawyer Robert M. Hughes III showed Davenport a photograph of a Johns-Manville asbestos carton with a warning in blue letters.

"Do you see the word "caution?" "Yes," Davenport said.

"Having looked at the photograph," Hughes said, "are you prepared to say that warning wasn't on the packages of Thermobestos (a Johns-Manville product used to insulate pipe at the refinery?"

"You misunderstand me," Davenport said. "I didn't say it wasn't on it. I didn't see it."

Last week, Judge Kellam dealt a damaging blow to Dishner's case. He ruled that Dishner's lawyers could not introduce evidence that Johnsville "fraudulently concealed" asbestos hazards as far back as 1949.

Kellam's decision means that Dishner's case will be limited by two-year statute of limitations in Virginia. Under that limitation, Dishner's lawyers will be able only to claim that the firm was liable from March 1975 - six months before Dishner, ill with mesothelioma, retired.

The Johns-Manville lawyers, when they present their case, are expected to argue that by that time, the hazards of asbestos were so widely known that the firm had no duty to warn Dishner.

Most of the asbestos cases, even though they involve Virginia law, have been assigned to federal court because the plaintiffs and defendants are from different states.