Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants. They are found through environment in the air, in the soil, in water, in plants, and also in food. PAHs are formed during pyrolisis and the incomplete combustion of organic materials. PAHs can be man-made or occur naturally. They undergo metabolic activation after entering the mammalian cells to highly toxic reactive metabolite intermediates and can irreversibly damage cellular macromolecules (DNA, proteins, lipids). Polycyclic aromatic hydrocarbons represent a class of toxicological compounds which can create a variety of hazardous effects in vivo, including cytotoxicity, genotoxicity, immunotoxicity, teratogenicity and carcinogenesis described in present paper.