N-nitroso compounds were found to be carcinogenic in 22 animal species. The organotropism of the carcinogenic action may be related to a variety of organs and organ systems. It does not only depend on the chemical structure of the molecules but also on the daily dose. It is highly probable that N-nitroso compounds also act carcinogenically in human beings. Predictions as to the organotropism of the carcinogenic action in man cannot be made. N-nitroso compounds have to be regarded als ‘multipotent’.