This article reviews the current status of lattice-dynamical calculations i
n crystals, using density-functional perturbation theory, with emphasis on
the plane-wave pseudopotential method. Several specialized topics are treat
ed, including the implementation for metals, the calculation of the respons
e to macroscopic electric fields and their relevance to long-wavelength vib
rations in polar materials, the response to strain deformations, and higher
-order responses. The success of this methodology is demonstrated with a nu
mber of applications existing in the literature,