This guidance recommends steps manufacturers and applicants of active pharmaceutical ingredients (APIs) and drug products should take to detect and prevent unacceptable levels of nitrosamine impurities in drug products. The guidance also describes conditions that may introduce nitrosamine impurities. The unexpected finding of nitrosamine impurities, which are probable or possible human carcinogens, in certain drug products has made clear the need for a risk assessment strategy for the potential presence of nitrosamines in any drug product.