The distribution of 14C-dotriacontane-16,17 and its combustion and pyrolytic products in cigarette smoke is described. Twenty-one percent of the activity is found in the mainstream smoke, 49 % is found in the sidestream smoke, and 30 % is found in the butt. Of the mainstream activity, 95 % is in unchanged dotriacontane. The transfer of 14C-dotriacontane to mainstream smoke is linear throughout the smoking of the cigarette, as shown by puff-by-puff data. Hypotheses to explain the results are presented