Descriptive and exploratory, retrospective study, conducted from the collection of the records of patients in a hematological unit of a large hospital in the city of Divinopolis, Minas Gerais, Brazil, with the aim of identifying risk factors in the use of antimicrobials in from January 2010 to December 2012. based on the factors identified were proposed bioethical reflections based on the principle of non-maleficence, focusing on the issue of bacterial resistance. Been identified as risk factors, the lack of adoption of precautionary measures according to the type of microorganisms, the empirical use of antimicrobials, the non-solicitation of antibiogram culture, lack of adherence to institutional protocols for infection control service and prolonged hospital stay. The results showed risk situations that demonstrate the irrational use of antimicrobial agents in the institution studied, leading to risks and even damage to patients and contributing to the increase in bacterial resistance. We stress the importance of investment in research and production of new antimicrobials, however, should be adopted control measures and prevention of risks associated with improper use of them, professional, and institutional awareness of society itself.