  The first part of this paper aims at illustrating the intense scientific
activity in the field of stellar rotation although, for sake of shortness, we
cannot be exhaustive nor give any details. The second part is devoted to the
rotation as a pertubation effect upon oscillation frequencies. The discussion
focuses on one specific example: the p-modes frequency small separation which
provides information about properties of the stellar inner layers. It is shown
that the small separation can be affected by rotation at the level of 0.1-0.2
microHz for a 1.4 Mo model rotating with an equatorial velocity of 20 km/s at
the surface. This is of the same order of magnitude as the expected precision
on frequencies with a 3 months observation and must therefore be taken into
account. We show however that it is possible to recover the small separation
free of these contaminating effects of rotation, provided enough high quality
data are available as will be with space seismic missions such as Eddington.
