CRYSCOR: a program for the post-Hartree-Fock treatment of periodic systems. CRYSCOR is a program performing electronic structure calculations for 1D-, 2D- and 3D-periodic non-conducting systems at the correlated level (presently local second order Møller-Plesset Perturbation Theory — LMP2). It uses the Hartree-Fock solution provided by the periodic LCAO-code CRYSTAL. The local correlation scheme is similiar to that applied in the corresponding molecular techniques, e.g. in the MOLPRO package. Two-Electron integrals are efficiently calculated using the density fitting technique (for the close-by pair distributions) and the multipole approximation (for the distant pairs). The Dual Basis set scheme allows for an expansion of the virtual space with respect to that used in the reference HF calculation.