A new vector-search rotation function has been implemented in a computer program called OVIONE. The rotation search is followed by a refinement of the highest peaks from the rotation function, both procedures being carried out in Patterson space.

The subtraction of the contribution of already positioned molecules from an observed Patterson map has proved to be useful for the determination of the correct orientation of the remaining molecules in the asymmetric unit of the crystal cell. For this purpose, a new procedure that incorporates a difference Patterson map in the evaluation of a vector-search rotation function has been developed.

Image-seeking functions have proved to be useful tools in macromolecular crystallography. The application of these functions in the molecular-replacement method has been studied.

A fast method for fitting model electron densities into EM reconstructions is presented. This new procedure was inspired by a rigid-body refinement method used in macromolecular X-ray crystallography.