We consider the cooperative decay of incoherently pumped atoms in a
disordered medium, where light undergoes multiple scattering. It is shown that
the cooperation number, which determines the duration and amplitude of
superfluorescent impulses, is given by the number of atoms along a diffusive
trajectory of the light propagating through the medium. We also consider the
problem of reflection of a probe wave during cooperative emission.Comment: 12 pages, latex, to be published in Sov.Phys.JET