This document discusses using ontologies to integrate data across multiple model organism databases to enable cross-species queries of phenotypes and genotypes. It describes efforts to develop Uberon, a multi-species anatomy ontology, and phenotype ontologies to describe phenotypes in a standardized way. By semantically integrating these resources, researchers can search for phenotypes of interest and discover potential gene function and disease gene candidates by finding similar phenotypes across species. This will help enable more comprehensive knowledge discovery across model systems.