Recent advances in both the US and Europe were discussed at the symposium on genotoxic impurities in pharmaceutical synthesis, which emphasised the need for sponsors of new drug applications to put measures in place to reduce the risks associated with possible genotoxic impurities. These contaminants need further scrutiny beyond that of the more general International Conference on Harmonisation (ICH) Q3A/Q3B recommendations as conventional genotoxicity testing for medicinal compounds can fail to prove that they are safe. A more exact risk characterisation may be appropriate in some situations, but the symposium argued that the threshold of toxicological concern (TTC) should serve as the baseline for risk management. Several real-world examples were given to illustrate the process of pharmaceutical synthesis and the introduction and management of contaminants. New developments in regulation were also addressed, including the idea of a "staged threshold of toxicological concern," which is applicable to situations involving short-term administration, such as clinical trials.