Introduction: For many years, Ontologies have been available in many different forms, for example: classification schema, thesauruses, Authorized vocabularies, Terminologies and dictionaries. Terminology and knowledge resources are essential components of interoperability among disparate systems. So, this paper considered the ontology of UMLS (which was prepared by National Library Medicine of American and it is a part of Unified Medical Language System).In addition to, we evaluate whether names and relationships needed in biomedical informatics are present in the UMLS, and analyzed the compatibility between ontology of the biomedical domain (the UMLS semantic network) and two other Ontologies: the Upper Cyc Ontology (UCO) and WordNet.Methods: In this study which has been done by the documentary and library methods (print & digital existing documentatins) about comparison between the UMLS and the other Ontologies (such as WordNet and Cyc), we try to consider the works 's like Burgun and Bodenereider, who surveyed on this field (and extracted the words which are related to the Biomedical informatics), in order to show the existence of relationships between them, as well as to determine and map them to the concept's of UMLS, and it΄s resources of it.Cyc categories that had no equivalent in the UMLS were integrated in our representation of the UMLS in order to build structure that was consistent with Cyc. They represent: Intermediate nodes, such as Primate (#$ genls Person Primate), (#$genls Primate Mammal) Generic concepts, such as simple repairing which is a super type of medical treatment event. Additional knowledge, such as biological taxon which provides information about biological categories, according to the general taxonomy of living beings.Analyzing in WordNet was held in two categories of Animal and Health disorder. Results: Roughly 50 Cyc categories were used for strictly covering the UMLS Semantic Network field. Approximately half of them were similar in both systems, for example Fish is similar in Cyc and in the UMLS. For the others, there was overlap between the Cyc and semantic network of UMLS. Thus it maps totally neither genetic function nor cell or molecular dysfunction in UMLS. Representation of anatomy differs, since elements of Cyc category Animal Body Region may be unhealthy body regions such as blisters, puncture wounds, which are abnormalities in the UMLS. In Cyc, Animal body part is a subtype of animal body region that includes both organs and body systems.For several UMLS semantic network (e.g. chemicals), there was no equivalent category in the public version of Upper Cyc Ontology. Additional the set of 11,634 UMLS concepts from the ANIMAL class was mapped to WordNet, whose ANIMAL class contains 3,984 synsets. 2,154 concepts (19%) were found in WordNet, 73% of them in the WordNet ANIMAL class. The UMLS Health disorder class contains more than 140000 concepts, which were mapped to WordNet, 2,639 UMLS concepts (2%) were found in WordNet, and among them, 1,257 concepts (48%) belonged to the WordNet health disorder class. Conclusion: There is no standard ULO available yet.within a class, concepts may be categorized differently, even when the categories look similar.