Working with pathogens or genetically engineered micro-organisms is a potential hazard for scientists, health care workers, employees of pharmaceutical industry, and also for the environment. Carelessness, poor technique in the handling of infectious materials, needle sting or infectious aerosol exposure are the cause of laboratory acquired infection. Biosafety, corollary of biocontamination, is based on the combination of good microbiological techniques, facility design of the laboratory and safety equipment. So, four biosafety levels are appropriate for the operations performed and the hazard posed by the infectious agents.