  Rotation has a number of important effects on the evolution of stars. It
decreases the surface gravity, causes enhanced mass loss and leads to surface
abundance anomalies of various chemical isotopes. We have adapted the Cambridge
stellar evolution code to incorporate a number of different physical models for
rotation. We compare detailed grids of stellar evolution models along with
simulated stellar populations to identify the key differences between them.
  Models of rotationally-driven dynamos in stellar radiative zones have
suggested that magnetohydrodynamic transport of angular momentum and chemical
composition can dominate over the otherwise purely hydrodynamic processes. We
have adapted our purely hydrodynamic model to include the evolution of the
magnetic field. We consider what effects this has on our populations of
rotating stars and how these relate to observational data.
  Strong magnetic fields are also observed at the end of the stellar lifetime.
The surface magnetic field strength of white dwarfs is observed to vary from
very little up to 10^9G. We look at how the strongest magnetic fields in white
dwarfs may be generated by dynamo action during the common envelope phase of
strongly interacting binary stars.
