The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that belongs to the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family. Its ligands include many natural and synthetic compounds, some of which, such as polyhalogenated aromatic hydrocarbons and polycyclic aromatic hydrocarbons, are important environmental contaminants. NF-kappaB is a pleiotropic factor that regulates many physiological and pathophysiological processes including the immune and inflammatory responses. In the past decade, accumulating evidence suggests close interactions between AhR and NF-kappaB pathways, and these interactions are potentially important mechanisms for many pathological processes such as the chemical-induced immune dysfunctions, carcinogenesis and alteration of xenobiotic metabolism and disposition. AhR-NF-kappaB interaction has become a mechanistic linchpin linking certain pathological responses induced by environmental insults. Furthermore, the AhR-NF-kappaB interaction provides basis for therapeutic applications of certain AhR ligands to treat human diseases. The effects of AhR-NF-kappaB on the epigenome are an important area that is not well understood. In this review, I highlight current research regarding the AhR-NF-kappaB(RelA) interactions with emphasis on the epigenetic impacts of these interactions on chromatin modifications and transcription elongation control.