In order to identify drug targets of some diseases, it is necessary to identify factors that control pathological conditions. In pathology, pathological conditions are viewed as morphological changes. Pathological diagnosis is based on these morphological changes, and pathologists are the ones who perform daily pathological diagnosis while witnessing pathological conditions. In this sense, pathologists could imagine the pathological control mechanism behind the morphological changes through the routine pathological diagnosis. Recently, the genetic analysis and bioinformatics have advanced dramatically, and we could easily obtain the candidates of factors controlling various disease conditions. However, it is necessary to go back to pathological specimens to verify the function of genes and factors. Pathology would be a discipline that directly relates to the elucidation of mechanism through direct contact with lesions. Of course, simple verification of factors regulating disease conditions in pathology specimens is one-sided. Such factors can become drug targets only when their pharmacological functions can be clarified. In this sense, collaboration between pathology and pharmacology is important to advance drug discovery research.