As part of the toxicological support for the use of ingredients on tobacco products there is a requirement in the UK to assess the genotoxic properties of the ingredients by testing the smoke condensate from a reference cigarettes containing the ingredients of interest. In these assessments, there are issues not usually encountered during the testing of developmental products in other industries. Smoke condensate from tobacco, in the absence of any ingredients, has been demonstrated to be a positive mutagen in the core in vitro genotoxicity systems detailed in regulatory guidelines (Ames, chromosome aberrations and mammalian cell mutation). Specifically, the potential effects of tobacco ingredients have to be evaluated against this background of activity from the tobacco smoke condensate itself. Mixtures of flavour ingredients have been added to a tobacco blend and a series of seven non-ventilated cigarettes made as well as a control cigarette without the added ingredients. The smoke condensates from these cigarettes have been Ames tested as recommended by the UK Scientific Committee on Tobacco and Health¹. The data has been analysed and demonstrates no additional activity of the condensates from the flavoured cigarettes above that of the control products. ¹. Report of The Scientific Committee on Tobacco And Health HMSO 1998. ISBN 011322124 X