For more than 20 years, since it was first published in 1983, the Laboratory biosafety manual has provided practical guidance on biosafety techniques for use in laboratories at all levels. Good microbiological technique and appropriate use of biosafety equipment by well trained staff remain the fundamental elements of laboratory biosafety. However, globalization, significant advances in technology, the emergence of new diseases and serious threats arising from the deliberate misuse and release of microbiological agents and toxins have necessitated a review of current procedures. For this new edition, therefore, the manual has been extensively revised and expanded. The manual now covers risk assessment and the safe use of recombinant DNA technology, and provides guidelines for the commissioning and certification of laboratories. Biosecurity concepts are introduced, and the latest international regulations for the transport of infectious substances are reflected. Material on safety in health-care laboratories, previously published elsewhere by WHO, has also been incorporated. It is hoped that the manual will continue to encourage countries to implement biological safety programmes and national codes of practice for the safe handling of potentially infectious materials.