  I review basic observational features in Population I stars which strongly
implicate rotation as a mixing agent; these include dispersion at fixed
temperature in coeval populations and main sequence lithium depletion for a
range of masses at a rate which decays with time. New developments related to
the possible suppression of mixing at late ages, close binary mergers and their
lithium signature, and an alternate origin for dispersion in young cool stars
tied to radius anomalies observed in active young stars are discussed. I
highlight uncertainties in models of Population II lithium depletion and
dispersion related to the treatment of angular momentum loss. Finally, the
origins of rotation are tied to conditions in the pre-main sequence, and there
is thus some evidence that enviroment and planet formation could impact stellar
rotational properties. This may be related to recent observational evidence for
cluster to cluster variations in lithium depletion and a connection between the
presence of planets and stellar lithium depletion.
