Recent results on uniqueness and stability of identification of coeffi
cients and right sides of partial differential equations from overdete
rmined boundary data are described. Elliptic, hyperbolic, and paraboli
c equations and scattering theory are considered. Proofs are given or
outlined whenever they contain a new and fruitful idea and are suffici
ently short. This review is supposed to be quite comprehensive. In fac
t, we do not cover only inverse spectral theory. Some interesting nume
rical methods are mentioned, but numerics is also beyond the scope of
this paper. A significant part is dedicated to so-called many boundary
measurements (equations with given Dirichlet-to-Neumann map), but we
also discuss results about single boundary measurements. An extensive
bibliography contains basic papers in the field.