We have implemented in TOM/FRODO a protein crystallographic symmetry display and handling package, called CRYStallize. This package is designed as an aid in solving protein structures by molecular replacement methods. It allows the rotation/translation solutions provided by molecular replacement programs to be checked in a fast and easy way. Using CRYStallize, approximate solutions can also be improved by manual modifications. Symmetry-related objects, represented as surfaces, can be generated and handled in the same way as the reference molecules, thus permitting an efficient analysis of crystal packing and site accessibility. This program is available in the TOM/FRODO software release, which runs on the Silicon-Graphics workstations.