MPATH is segmented into two sections, one containing classes of pathological process and the second pathological entities, ie lesions. The organisation within each segment is primarily at the level of general pathology and within each section are areas covering special pathology and organ specific pathobiology.The ontology is designed to be used by making cross-products with the relevant species specific anatomy ontologies or the cell ontology to cover the organ-specific instances of lesions, and the PATO ontology can be used to add information concerning microscopic morphological, grade and severity qualifiers. MPATH is currently primarily being used to capture diagnostic information on mouse pathological lesions and in constructing the logical definitions for higher order phenotype classes in the human and mammalian phenotype ontologie