Motivation: To provide a graphical interface for the generation display and manipulation of a sequence landscape that will run on all X-windows-based Unix workstations. Results: The sequence landscape approach enables the representation of the frequency of occurrence of all query sequence sub-words within a database. The landscape approach can detect tandem and other repeating word motifs, specific sub-words that are often represented words in a particular database using Markov probability and the preference for sub-words belonging to either one of two databases. All these features aid in the classification of a query sequence. Given the open-text format for sequences and databases, the Xlandscape tool can be applied to a wide range of problems. Availability: Xlandscape is freely available by anonymous ftp to beagle.colorado.edu, directory, pub/landscape/xland.vl.tar.Z. Contact: Samuel.Levy@@@colorado.edu or Gary.Stormo@@@colorado.edu.