  Many observational results seem to indicate more efficient mixing processes
in intermediate mass stars (5-20 M$_{\odot}$) than the expected by the standard
models. These processes are usually thought to be caused by stellar rotation.
Our recent analysis of 19 evolved intermediate mass stars has found them to
display different efficiencies of internal mixing. The comparison of these
results, and others from the literature, with rotating and non-rotating stellar
evolutionary models led us to find, for the first time, an important
correlation between stellar mass and the [N/C] ratio; the kind of correlation
expected to be produced by a rotation-induced mixing.
