  The global fit of the Standard Model to electroweak precision data, routinely
performed by the LEP electroweak working groups and others, has been revisited
in view of (i) the development of the new generic fitting package, Gfitter,
(ii) the insertion of constraints from direct Higgs searches at LEP and
Tevatron, and (iii) a more thorough statistical interpretation of the results.
This paper describes the Gfitter project, and presents state-of-the-art results
for the global electroweak fit in the Standard Model, and for a model with an
extended Higgs sector. Example results are an estimation of the mass of the
Higgs boson (M_H = 116.4^{+18.3}_{-1.3} GeV) and a forth-order result for the
strong coupling strength (alpha_S(M_Z^2) =
0.1193^{+0.0028}_{-0.0027}(exp)+/-0.0001(theo)). Using toy Monte Carlo
techniques the p-value of the SM has been determined (p=0.22). As an example of
a New Physics model constraints are derived for the Two Higgs Doublet Model of
Type-II using observables from the B and K physics sectors.
