All the evidence obtained in our laboratories has shown that the total aldehyde yield in tobacco smoke is not related to either sugar content or the equilibrium moisture content of the tobaccos. There is, however, a relationship between particulate matter [PM(WNF)]+ and aldehyde delivery. This accounts for some 41 % of the total variation between different cigarettes. + PM(WMF) = Total particulate matter - (water + nicotine)