  In order to investigate the possible influence of rotation on the efficiency
of the first dredge-up we determined atmospheric parameters, masses, and
abundances of carbon, nitrogen, and oxygen in a sample of evolved intermediate
mass stars. We used high resolution spectra and conducted a model atmosphere
analysis. The abundances were calculated through spectral synthesis and
compared to the predictions of rotating and non-rotating evolutionary models.
Almost all those objects in our sample where carbon and nitrogen abundances
could be determined show signs of internal mixing. The stars, however, seem to
be mixed to different extents. Among the mixed stars we identify five in our
sample with abundances in agreement with the non-rotating models, four stars
that seem to be mixed beyond that, and one star that seems to be slightly less
mixed than predicted for the first dredge-up. There are also five stars that
seem to be slightly more mixed than expected, but their abundances are in
marginal agreement with both rotating and non-rotating models. Such differences
in the extent of the mixing are not predicted by the standard models and imply
the action of other mixing mechanisms than solely the convective dredge-up. We
also identified for the first time an important correlation between the [N/C]
ratio and the stellar mass.
