IV
  To summarize:  -general acceptance- is not a necessary precondition
to the admissibility of scientific evidence under the Federal Rules of
Evidence, but the Rules of Evidence-especially Rule 702-do assign to
the trial judge the task of ensuring that an expert's testimony both
rests on a reliable foundation and is relevant to the task at hand.
Pertinent evidence based on scientifically valid principles will
satisfy those demands.
  The inquiries of the District Court and the Court of Appeals focused
almost exclusively on -general acceptance,- as gauged by publication
and the decisions of other courts.  Accordingly, the judgment of the
Court of Appeals is vacated and the case is remanded for further
proceedings consistent with this opinion.
                                      It is so ordered.
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