Abstract: Knowledge about human beings is an integral part of anyintelligent agent of considerable significance. Delimiting, modelingand acquiring such knowledge are the central topics of this paper.Because of the tremendous complexity in knowledge of human beings,we introduce a top-level ontology of human beings from theperspectives of psychology, sociology, physiology and pathology. Thisontology is not only an explicit conceptualization of human beings, butalso an efficient way of acquiring and organizing relevant knowledge.