  In the last decade, it has been possible to monitor variable X-ray sources in
nearby galaxies. In particular, since the launch of Chandra, M31 has been
regularly observed. It is perhaps the only nearby galaxy which is observed by
an X-ray telescope regularly throughout operation. With 10 years of
observations, the center of M31 has been observed with Chandra for over 1 Msec
and the X-ray skies of M31 consist of many transients and variables.
Furthermore, the X-ray Telescope of Swift has been monitoring several
ultraluminous X-ray sources in nearby galaxies regularly. Not only can we
detect long-term X-ray variability, we can also find spectral variation as well
as possible orbital period. I will review some of the important Chandra and
Swift monitoring observations of nearby galaxies in the last decade. I will
also discuss the possibility to use MAXI for X-ray monitoring observations of
nearby galaxies.
