The distribution of six radiolabelled model flavourants in cigarette smoke has been described. The possibility of pyrolytic products occurring in the mainstream smoke has been thoroughly examined. Of the six flavourants used four showed no detectable decomposition. Anisaldehyde underwent some decomposition that was detectable in the mainstream smoke. Even so the major radiolabelled smoke product was unchanged anisaldehyde (91.4 %). Vanillin decomposition, although suspected, was only detected in the sidestream gases in these experiments.