This experiment has been performed to clarify the question to which extent fractions containing polycyclic aromatic hydrocarbons (PAH) or other carcinogenic compounds are responsible for the biological activity of cigarette smoke condensate. With chromatographic procedures using organic gels it was possible to separate quantitatively polar compounds from the PAH-fraction and to obtain fraction IX representing 0.4% of the whole condensate. In this fraction the PAH were enriched 250fold. Significant losses of tumorigenic effects by this fractionation method could not be observed. This PAH-containing fraction showed 50% of activity compared with the overall activity of whole smoke condensate of a reference cigarette. A so-called PAH-free fraction showed with 7% of the overall activity of the whole smoke condensate a weak carcinogenic effect. The importance of PAH for the tumorigenic effect of cigarette smoke is emphasized by these results.