4th edition The WHO Laboratory Biosafety Manual (LBM) has been in broad use at all levels of clinical and public health laboratories, and other biomedical sectors globally, serving as a de facto global standard that presents best practices and sets trends in biosafety. LBM encouraged countries to accept and implement basic concepts in biological safety and to develop national codes of practice for the safe handling of biological agents in laboratories within their geographical borders. This fourth edition of the manual builds on the risk assessment framework introduced in the third edition. A thorough, evidence-based and transparent assessment of the risks allows safety measures to be balanced with the actual risk of working with biological agents on a case-by-case basis. This novel evidence- and risk-based approach will allow optimised resource use and sustainable laboratory biosafety and biosecurity policies and practices that are relevant to their individual circumstances and priorities, enabling equitable access to clinical and public health laboratory tests and biomedical research opportunities without compromising safety.