GEOMETRY is a software package for the analysis of nucleotide sequences using the method of statistical geometry in sequence space. The package consists of programs performing estimation of the average geometry of sequence quartets, analysis of positional variability and computer simulation of parallel and tree-like sequence divergence with user-defined parameters. It provides an independent tool for evaluation of the reliability of conventional phylogenetic trees and calibration of the time of sequence divergence. GEOMETRY may be of interest for all scientists engaged in the study of molecular phylogeny. The package is available by anonymous FTP from ftp.bionet.nsk.su, directory /incoming/molevol/geom.exe, and will be available from EMBL file server (URL: http://@www.ebi.ac.uk)