  With the construction of the VLTI (Very Large Telescope Interferometer of the
European Observatory ESO for the southern hemisphere) it is now possible to
make observations with resolutions of the order of milli-arc-seconds,
especially in IR with AMBER instrument (Astronomical Multi Beam Recombine).
These new capabilities allow us to better constrain the stellar structures such
as polar jets, equatorial disks and flattened photospheres of rotating stars.
Thus the estimation of stellar fundamental parameters allows to explore in
detail the mechanisms of mass loss, pulsation and magnetism governing the
variability and the evolution of the stars.
  This thesis presents the results of fast rotating stars observations carried
out on the AMBER spectro-interferometer VLTI in its high \& medium spectral
resolutions modes. The observations were highly degraded by the optical defects
of AMBER and their analysis required the development of specific digital
reduction tools to reach the necessary precision for the interferometric
measurements interpretation. In order to interpret those measures I developed a
chromatic semi-analytical model of rapidly rotating star that allowed me to
estimate, from the differential phases; the degree of flattening, the
equatorial radius, the rotation velocity, the angle of inclination, the
position angle of the star rotation axis in the sky, the local distribution of
the effective temperature and the surface gravity of the star within the von
Zeipel theorem. The results for four massive stars of spectral types B, A and F
have allowed me to characterize the mechanisms discussed above and thus open
some prospect for more systematic studies of similar objects, with extending
later these studies to the relationship photosphere - circumstellar envelope.
