The method consisted in comparing petroleum ether soluble tar of pure tobacco with tar of the same tobacco previously washed in petroleum ether. Comparison was also made of soluble tar of pure cellulose cigarettes with tar of cellulose cigarettes impregnated with tobacco extract. The average actual transfer level of tobacco petroleum ether solubles was 40-45% in the mainstream smoke. This level was calculated from tobacco consumed during puffs. The incidence of petroleum ether extract on the pyrogenesis of polycyclic aromatic hydrocarbons in smoke, is therefore, less important than the pyrolysis tests had led to believe. On the other hand, the authors showed that the fraction of tar soluble in petroleum ether was, in both quality and quantity, linked to the petroleum ether extracts of tobacco and that the organo-soluble constituents transferred from tobacco without transformation, could represent more than 20% of the anhydrous condensates of the mainstream smoke.