It tells a study carried through in the Library of Pós-Graduação em Odontologia CCS/UFPB that had as objective to evaluate the relevance of the Database BBO (Brazilian Bibliography of Dentistry) and the effectiveness of the quantity of the library. As methodology the criterion was used the coefficient of precision applied for Lancaster to measure performance in information systems. During a period of six months it was collected data on the searches made in the related Base, through a form in which the users requested the information survey on the subject of their research, it was printed a matter list with the recouped registers and repassed to the user to indicate which itens would be pertinentto the necessity of information. The searches were carried through by the proper users with the orientation of librarians. 1008 registers of these 840 had been recouped and considered pertinent by the users, thus getting a mean accuracy of 83% of the results. One another data raised in the research was in relation t o the relevancy of the actual quantity of the Library`s itens excellent for the user, 720 of them was available in the quantity, the percentage of 86% This study evidenced the importance of the BBO, for the consistency in the boarded subjects and for the efficiency in its strategy of search that facilitates the recovery of the information, as well as, the relevancy of the quantity of the library.