The retention by humans of 20 polycyclic aromatic hydrocarbons (PAHs) from mainstream cigarette smoke was evaluated. The analysis was done by a new technique using solid phase extraction (SPE) for the cleanup and the conservation of PAHs. The new technique has excellent sensitivity and accuracy, which were necessary for the analysis of the very low levels of PAHs present in the exhaled cigarette smoke. The study was done on a common commercial cigarette with 10.6 mg 'tar' by U.S. Federal Trade Commission (FTC) recommendation. The results were obtained from ten human subjects, each smoking three cigarettes. The exhaled smoke was collected using a vacuum assisted procedure that avoids strain in exhaling. The study showed that the PAHs with a molecular weight lower than about 170 Daltons are retained with high efficiency. The heavier molecules are less retained, but even compounds such as indeno [ 1,2,3 -cd]pyrene, dibenz[a,h]anthracene, and benzoperylene are retained with efficiencies around 50%. The dependence of retention efficiency for PAHs (in %) on their octanol-water partition coefficient (LogPow) was found to be nonlinear and showed considerable variability for several compounds that have very close LogPow values. Better correlation was obtained between the retention efficiency and PAHs vapor pressure (Log VP).