Federal officials have found Dr. Robert C. Gallo, the government`s most prominent AIDS researcher, guilty of scientific misconduct for deliberately concealing his laboratory`s experiments with an AIDS virus discovered in France nearly a decade ago.

Department of Health and Human Services officials notified Gallo Tuesday of their conclusion that he knowingly falsified a key portion of a landmark 1984 scientific article stating that the French virus had never been grown successfully. Gallo condemned the finding.

According to a new 62-page HHS report on the long-running Gallo case, at the time the article was published the French virus, called LAV, had grown both in Gallo`s National Cancer Institute laboratory and at the Pasteur Institute of Paris, where it was discovered in 1983.

Contradictions between Gallo`s published statements and laboratory records showing his laboratory`s growth of LAV were first noted in a 1989 Chicago Tribune article on the history of the discovery of the AIDS virus.

The Tribune article also concluded that, either because of accident or theft, the Gallo lab`s principal AIDS virus isolate, called HTLV-3B, is actually the French LAV. The HHS report maintains that ''it is not possible to resolve the question'' of whether this happened through a deliberate theft or an accidental laboratory contamination.

In finding Gallo guilty of scientific misconduct, the HHS report concludes that Gallo`s published assertions not only ''virtually ensured'' his own laboratory`s preeminence in AIDS research but ''impeded potential AIDS research progress'' with the French virus.

The HHS report, a copy of which was made available to the Tribune, also noted that, in addition to the falsification, ''many of Dr. Gallo`s (other)

actions reflect a pattern of conduct that must be censured even though they do not constitute scientific misconduct.''

The report said these include ''Dr. Gallo`s propensity to misrepresent and mislead in favor of his own research findings or hypotheses,'' failure to meet the obligation for scientific accuracy, ''irresponsible laboratory management,'' and ''indifference to acknowledging promptly the contributions of others and to sharing of research materials of critical public health importance.''

Although the HHS report acknowledged the role of Gallo`s laboratory in helping to identify the AIDS virus and developing the American AIDS blood test, it concluded that ''to have these critical accomplishments diminished by the actions documented in this investigation is a tragedy for science. . . . ''

The HHS report noted that, ''because of Dr. Gallo`s senior status and his highly visible role in the research community, the finding of scientific misconduct by itself carries a high degree of opprobrium.''

But HHS officials also directed that, should their findings be upheld on appeal, the National Institutes of Health (NIH) develop ''a plan to ensure accuracy in the recording and reporting of research'' conducted by Gallo`s laboratory over the following three years.

The verdict against the controversial researcher, who narrowly escaped a similar misconduct sanction last year, is the latest in a series of twists and turns by government officials in attempting to assess Gallo`s responsibility for false and misleading scientific reports from his lab.

The National Institutes of Health, of which the cancer institute is a part, concluded earlier this year that Gallo had not committed scientific misconduct. It was in the course of reviewing the NIH`s two-year investigation that the HHS`s Office of Research Integrity overturned the NIH`s conclusion.

Gallo called the HHS misconduct finding ''utterly unwarranted'' and said he intended to appeal. He said the lengthy investigation of his research, which he termed ''endless and incompetent,'' should be ''of concern to everyone seeking to advance medical knowledge.''

NIH Director Bernadine Healy, who last March endorsed the initial not-guilty verdict in the Gallo case, said in a statement Wednesday that she had reached that conclusion ''based on the facts as they were presented to me after a lengthy investigation.'' Healy acknowledged that ''new facts or new interpretations may lead others to come to a different conclusion.''

Gallo, who heads one of the NIH`s biggest laboratories and is among its most honored scientists, is by far the most senior NIH researcher ever to have been found guilty of laboratory misconduct.

The determination that Gallo knowingly falsified the status of AIDS research in his laboratory also marks the first time HHS officials assigned to review scientific misconduct cases have reversed a finding of no misconduct by the NIH.

In addition to representing a slap at NIH Director Healy, who earlier this year urged that ''reasonable attempts must be made to clear Dr. Gallo`s reputation with regard to accusations of misconduct,'' the HHS report appeared to vindicate a panel of distinguished scientists chosen by NIH to review the Gallo case.

That group, known as the Richards committee after its chairman, Yale biologist Fred Richards, gave Healy a scathing report that accused Gallo of several instances of scientific misbehavior, including the ''intellectual appropriation'' of the French AIDS virus. Healy ignored the Richards report.

The focus of the Gallo investigation is the assertion in his celebrated 1984 article, published in the journal Science, that the French AIDS virus had ''not yet been transmitted to a permanently growing cell line for true isolation and therefore has been difficult to obtain in quantity.''

In the first such official acknowledgment ever, the HHS report concedes that, whether knowingly or not, Gallo`s lab actually used a LAV sample sent by Pasteur researchers in all of its critical AIDS experiments, including those leading up to and including the development of the American blood test for AIDS.

Citing new evidence that its AIDS virus has been used since 1985 in the development and manufacture of the American AIDS test, the non-profit Pasteur Institute has asked the Bush administration to cede it all future royalties from the government-owned patent on that test, a total of about $3 million a year.

Administration officials have said they will make a decision on the French request when the Gallo investigation has been resolved. A Pasteur spokesman said Wednesday that the institute`s representatives intended ''to return immediately to the U.S. government and ask that it do the right thing.''

Federal investigators were astonished to discover last year that although Dr. Mikulas Popovic, then Gallo`s chief virologist, had accurately described his experiments with the French virus in his initial draft of the Science article, Gallo had taken the description out, appending the marginal notation, ''Mika, you are crazy.''