Carcinogenic N-nitrosamines (NA) can be formed from a wide range of nitrogen-containing substances and nitrosating agents directly in environmental objects and living organisms. The ease of formation, rather high reactivity and stability of NА determine their significant distribution in the environment and the possibility of undesirable effects on humans. This paper presents data of the detection and quantitative content of NA in the air, drinking and waste water, soil, mineral nitrogen fertilizers and pesticides, products of the chemical and rubber industry, medicines, animal feed, food products. Mainly, such NA as N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosomorpholine, N-nitrosopyrrolidine, N-nitrosopiperidine, N-nitrosopropylamine, N-nitrosodibutylamine were found.