  We investigate the long-term variability exhibited by the X-ray point sources
in the starburst galaxy M82. By combining 9 Chandra observations taken between
1999 and 2007, we detect 58 X-ray point sources within the D25 isophote of M82
down to a luminosity of ~ 10^37 ergs/s. Of these 58 sources, we identify 3
supernova remnant candidates and one supersoft source. Twenty-six sources in
M82 exhibit long-term (i.e., days to years) flux variability and 3 show
long-term spectral variability. Furthermore, we classify 26 sources as
variables and 10 as persistent sources. Among the total 26 variables, 17 varied
by a flux ratio of > 3 and 6 are transient candidates. By comparing with other
nearby galaxies, M82 shows extremely strong long-term X-ray variability that
47% of the X-ray sources are variables with a flux ratio of > 3. The strong
X-ray variability of M82 suggests that the population is dominated by X-ray
binaries.
