Biosafety in Microbiological and Biomedical Laboratories (BMBL) has served as the cornerstone of biosafety practice in the United States since its initial release in 1984. We wish to emphasize that the sixth edition of BMBL remains an advisory document recommending best practices for the safe conduct of work in biomedical and clinical laboratories from a biosafety perspective. The BMBL is not intended to be a regulatory document, although we recognize that some may use it in that way. The core principle of this document is protocol-driven risk assessment; it is not possible for a single document to identify all of the possible combinations of risks and mitigations feasible in biomedical and clinical laboratories. The BMBL should be used as a tool in the assessment and proposed mitigation steps in biomedical and clinical laboratories.