Comparative Mapping by Annotation and Sequence Similarity (COMPASS) has been demonstrated to be an effective approach for predicting the chromosome location of expressed sequence tags (ESTs) and other sequence-based markers on the basis of comparative mapping information. Herein, we describe the development and use of a computer program to execute the COMPASS strategy en masse. The program was used to identify orthologs and predict map locations of 47,787 cattle ESTs. Among these 47,787 ESTs, 30,097 had significant matches with sequences in the human UniGene database and 21,311 were annotated with human GB4 radiation hybrid mapping data. These sequences are contained within 9,956 and 6,295 individual human UniGene clusters, respectively. The putative human orthologs and predicted cattle chromosome locations of the 21,311 cattle ESTs with GB4 mapping data are provided in this report as a resource for the research community.