  Massive stars define the upper limits of the star formation process, dominate
the energetics of their local environs, and significantly affect the chemical
evolution of galaxies. Their role in starburst galaxies and the early Universe
is likely to be important, but we still do not know the maximum mass that a
star can possess, i.e.``the upper mass cutoff.'' I will discuss results from a
program to measure the upper mass cutoff and IMF slope in the Galactic Center.
The results suggest that the IMF in the Galactic center may deviate
significantly from the Salpeter value, and that there may be an upper mass
cutoff to the initial mass function of $\sim$150 Msun.
