We present a geometric theory of the Fourier-Bros-Iagolnitzer transform on
a compact C-infinity manifold M. The FBI transform is a generalization of t
he classical notion of the wave-packet transform. We discuss the mapping pr
operties of the FBI transform and its relationship to the calculus of pseud
odifferential operators on M. We also describe the microlocal properties of
its range in terms of the "scattering calculus" of pseudodifferential oper
ators on the noncompact manifold T*M.