Is President John F. Kennedy's brain really missing from the National Archives? And what about those "secret" assassination files that can't be opened for another 37 years?

If you've seen "JFK," Oliver Stone's three-hour docudrama about a sinister conspiracy to kill the president, you might be wondering the same thing. Such questions have caused more than a few headaches at the National Archives, staff members said last week. The movie has generated a surge in public requests to inspect evidence relating to Kennedy's slaying.

"There's always been interest in this from Day One, but in the last few months we've been very busy," said Michael R. McReynolds, who, as director of the Textual Reference Division, oversees the records of the Warren Commission that in 1964 completed its investigation of the Nov. 22, 1963, Kennedy assassination. "We're getting a lot of letters from people asking for information and to see documents. Almost all of them want to see autopsy photographs."

As official custodian of the nation's records, the Archives retains hundreds of thousands of pages of Warren Commission records -- more than 360 cubic feet of material: from the Italian-made Mannlicher-Carcano rifle used by Lee Harvey Oswald to pictures of the strippers who worked at Jack Ruby's Dallas nightclub, the Carousel.

But while 98 percent of this material is theoretically open to the public, the businesslike McReynolds explained that you can't just wander in off the street and take a peek. Under an agreement with the Kennedy family, for example, the autopsy material has been restricted to "serious" researchers, and the Archives applies the same standard to material evidence.

"We have a lot of people who walk in and say, 'Can I see the rifle?' " said McReynolds, leading a reporter on a tour through the dimly lit rooms where the records are kept. "We say, 'No. . . . It's not a serious request.' "

Meanwhile, the Archives has accelerated its review of the remaining 2 percent of classified Warren Commission evidence, which is segregated in 20 boxes in a secure vault. McReynolds and other Archives officials indicated last week that at least some of that material will never be made public.

There are, for example, Oswald's tax returns. "That's protected by statute," said Jill D. Brett, an Archives spokeswoman.

But much of the interest generated by Stone's movie centers on another set of assassination documents also stored at the Archives: the unpublished records of the House Select Committee on Assassinations, turned over to the Clerk of the House in 1979 and sealed until the year 2029. Conspiracy theorists have long contended that these "secret" records -- not subject to the Freedom of Information Act -- hold critical clues to the assassination.

Among the 400 cubic feet of documents in the committee files, for example, are records of staff interviews, files on informants and, perhaps most intriguing, a 200-plus-page report written by a committee staff member about Oswald's trip to the Cuban and Soviet embassies in Mexico City a few months before the assassination.

James Lesar, a Washington lawyer who heads the privately funded Assassinations Archives and Research Center and who has been suing the government for more than a decade for release of the files, said he believes the report questions whether "it was Oswald that visited those embassies. And if it was not Oswald, then who the hell was it?"

Stone makes much of the "secret" files in "JFK," and when the director spoke before the National Press Club last week, his publicists passed out red, white and black "JFK Free the Files" buttons. Archives officials insist the sealing of those assassination committee records is not as suspicious as Stone makes it sound.

Under a House rule, all unpublished records of House committees are sealed from the public for 30 years, and certain categories -- such as minutes of executive session meetings -- are sealed for 50 years, said Bob Corren, who oversees committee records at the Archives. "Records of the Merchant Marine Committee . . . the Agriculture Committee, they're all closed," said Corren, who added that he has never taken a look at the JFK files.

Lesar and other committee critics say Rep. Louis Stokes (D-Ohio), who was chairman of the former House Select Committee on Assassinations, and the panel's chief counsel, G. Robert Blakey, have consistently opposed calls to release the files. But now, momentum to do so is mounting. Stokes last week said he was "exploring the possibility" of supporting a House resolution that would unlock the files.

Over at the Archives, staff members are more concerned about another assertion in Stone's movie -- in the epilogue -- suggesting that the Archives somehow lost the president's brain.

"It's important to us that we clear this up," said spokeswoman Brett.

The claim was first made by Cyril Wecht, a prominent Pittsburgh pathologist and longstanding Warren Commission critic, after he was permitted to examine Kennedy autopsy records at the Archives in 1972. An inventory of materials that had been turned over to Kennedy's former secretary, Evelyn Lincoln, at the National Archives by Kennedy's personal physician, George G. Burkley, in April 1965 had listed nine categories of autopsy-related items, including a "stainless steel container -- seven inches in diameter -- containing gross material" and microscopic tissue slides.

Wecht said that seven years later when he opened the material that had been locked in a footlocker, the stainless steel container and slides were gone. "There's something very sinister about this," Wecht said yesterday. "It's the most important piece of physical evidence in the case. At the very least, they {the Archives} were inept and negligent."

But Brett contends the charge is unfair. In fact, she said, the material turned over by Burkley belonged to the Kennedy family. She said that a few days after Burkley gave the material to Lincoln in 1965, a secretary to Sen. Robert F. Kennedy retrieved it. Not until Oct. 29, 1966, did Burke Marshall, a lawyer for the Kennedy family, return the material in a footlocker to the Archives and officially deed its contents to the government.

"We have no idea what happened to the gross material and tissue slides," said Brett. "But the point is they were never in the custody of the National Archives. . . . The movie implies they were part of the {Archives} records and that's not accurate."