  Rapid rotation enhances the dynamo operating in stars, and thus also
introducessignificantly stronger magnetic activity than is seen in slower
rotators. Many young cool stars still have the rapid, primordial rotation rates
induced by the interstellar molecular cloud from which they were formed. Also
older stars in close binary systems are often rapid rotators. These types of
stars can show strong magnetic activity and large starspots. In the case of
large starspots which cause observable changes in the brightness of the star,
and even in the shapes of the spectral line profiles, one can get information
on the rotation of the star. At times even information on the spot rotation at
different stellar latitudes can be obtained, similarly to the solar surface
differential rotation measurements using magnetic features as tracers. Here, I
will review investigations of stellar rotation based on starspots. I will
discuss what we can obtain from ground-based photometry and how that improves
with the uninterrupted, high precision, observations from space. The emphasis
will be onhow starspots, and even stellar surface differential rotation, can be
studied using high resolution spectra.
