  We use the rotating stellar models described in the paper by A. Maeder & G.
Meynet in this volume to consider the effects of rotation on the evolution of
the most massive stars into and during the Wolf--Rayet phase, and on the
post-Main Sequence evolution of intermediate mass stars. The two main results
of this discussion are the following. First, we show that rotating models are
able to account for the observed properties of the Wolf--Rayet stellar
populations at solar metallicity. Second, at low metallicities, the inclusion
of stellar rotation in the calculation of chemical yields can lead to a longer
time delay between the release of oxygen and nitrogen into the interstellar
medium following an episode of star formation, since stars of lower masses
(compared to non-rotating models) can synthesize primary N. Qualitatively, such
an effect may be required to explain the relative abundances of N and O in
extragalactic metal--poor environments, particularly at high redshifts.
