This guideline concerns the testing and evaluation of the viral safety of biotechnology products, and it outlines what data should be submitted in marketing application and registration packages for those products. Biotechnology products include biotherapeutics and certain biological products derived from cell cultures initiated from characterised cell banks of human or animal origin (e.g., mammalian, avian, insect). In this document, the term “virus” excludes non-conventional transmissible agents like those associated with mammalian prions (e.g., bovine spongiform encephalopathy, scrapie). Applicants are encouraged to discuss bovine spongiform encephalopathy-associated issues with the appropriate regulatory authorities.