Effect of carcinogenic polycyclic aromatic hydrocarbons (PAH) benzo(a)pyrene (BP) and 3-methylcholanthrene (MC) on transcription factor NF-kappaB activation was studied. The determination of NF-kappaB activity was performed by two different methods: determination of mRNA expression of NF-kappaB-dependent I-kappaB gene, and determination of transcription activity of co-transfected with the plasmid containing the luciferase reporter gene under the NF-kappaB-sensitive promoter. As a subject of inquiry the hepatoma cell cultures HepG2 expressed Ah receptor and G27 not expressed Ah receptor were used. BP and MC weekly enhanced NF-kappaB activity in proliferating HepG2 cells. The enhance of NF-kappaB activity was significantly higher in resting cells. NF-kappaB activation by BP and MC in hepatoma G27 cells was significantly higher in hepatima G27 cells than in HepG2 cells both in proliferating and resting cells. The role of Ah receptor in PAH action on NF-kappaB activation is discussed.