  HST imaging of M22 has allowed, for the first time, a detailed and uniform
mapping of mass segregation in a globular cluster. Luminosity and mass
functions from the turnoff down to the mid to lower main sequence are presented
for M22 in annular bins from the centre of the cluster out to five core radii.
Within the core, a significant enhancement is seen in the proportion of 0.5-0.8
M(sun) stars compared with their numbers outside the core. Numerical modelling
of the spatial mass spectrum of M22 shows that the observed degree of mass
segregation can be accounted for by relaxation processes within the cluster.
The global cluster mass function for M22 is flatter than the Salpeter IMF and
cannot be represented by a single power law.
