On the world-volume of an M-theory five-brane propagates a two-form wi
th self-dual field strength. As this field is non-Lagrangian, there is
no obvious framework for determining its partition function. An analo
gous problem exists in Type IIB superstring theory for the self-dual f
ive-form. The resolution of these problems and definition of the parti
tion function is explained. A more complete analysis of perturbative a
nomaly cancellation for M-theory five-branes is also presented, uncove
ring some surprising details.