The National Institutes of Health yesterday effectively cleared researcher Robert C. Gallo of the allegation that he stole the discovery of the AIDS virus from a fellow researcher.

The decision, which followed an 11-month investigation, apparently settles a controversy over Gallo's 1984 discovery that has divided the biomedical research community and cast a shadow over the accomplishments of the one of the country's most famous scientists.

"All of the major questions relating to the conduct and integrity of the laboratory have been eliminated," said a NIH researcher, who asked not to be named. "This is a tremendous victory for Gallo."

The special NIH investigation of Gallo, which began in November of last year, was prompted by news accounts and persistent allegations by other scientists that Gallo had not -- as he claimed -- discovered the AIDS virus, but had either accidentally or deliberately stolen the credit for the discovery from a French scientific team working in the same field.

But in a terse statement released yesterday after the longest inquiry in NIH history, acting NIH director William F. Raub said that the NIH's internal Office of Scientific Integrity had "resolved certain of the publicized allegations and issues or shown them to be without substance," including the principal question of whether Gallo had any motive to steal the French virus.

Raub said that some remaining issues in the Gallo investigation would now come under a full-scale investigation, and according to an NIH spokesman, those questions potentially could have serious implications for the Gallo laboratory. However, scientists familiar with the investigation said that the remaining issues were of far less significance.

"I think there is no question that this ought to remove all doubts from the major allegations that were made against Gallo," said Dani Bolognesi, a prominent AIDS researcher at Duke University.

"What remains is a mystery," said Bolognesi. "It is hard to imagine anything there that warrants going ahead with a full investigation. Maybe they are keeping something to themselves."

Allegations about possible misconduct concerning Gallo's discovery of the human immunodeficiency (HIV) virus first surfaced in 1985, when genetic analysis of the virus discovered by Gallo and an HIV virus discovered simultaneously by the Paris-based Pasteur Institute revealed them to be so similar as to suggest they came from the same blood sample.

Since the French team had sent Gallo an early sample of their virus for research purposes, some researchers alleged that what Gallo had discovered was -- either by accident or by deliberate manipulation -- simply a copy of the French virus.

Gallo settled his dispute with the French. But in the years since, fanned by critics within the scientific community and a 50,000-word investigative article in the Chicago Tribune last year, the allegations against Gallo have continued to mount, besmirching the reputation of a scientist frequently mentioned as a Nobel Prize contender and raising the extraordinary possibility that one of the most celebrated American scientific discoveries of the past decade was based on outright fraud.

Since the beginning, Gallo has stated that he had no reason to steal the French virus because his research team had isolated many other strains of HIV at the same time, each of which was undeniably different from the French strain and any one of which could sustain his claim to be the discover of the cause of AIDS.

Gallo's critics, however, have maintained that he had no other strains of HIV at that time and thus had a clear motive for stealing the French virus.

The NIH panel, after exhaustive interviews with Gallo and his researchers and a painstaking analysis of hundreds of pages of scientific data, came down squarely on Gallo's side. "The inquiry team has concluded that Dr. Gallo had a substantial number of HIV detections and isolations from several different sources at the critical time" that the French virus was growing in his laboratory, Raub said.

It is not clear what direction the Gallo investigation will now take. Raub declined to elaborate on the future inquiry beyond stating that the NIH would concentrate on two issues: "aspects of published reports" from Gallo's laboratory, particularly the first of four papers written by Gallo's laboratory for the journal Science in May 1984, and the question of the precise biological origins of the HIV isolate discovered by Gallo.

The Science paper in question is one of the most critical and admired accomplishments of the Gallo laboratory, laying down the basic methods for the creation of the HIV blood test now used throughout the world. And the question of where Gallo's isolate came from is, given the NIH's stand on the existence of other isolate, largely an academic question, scientists said.