Cancer ranks among the most serious health and economic problems in developed countries. Carcinogenesis consists in accumulation of damaged genes for certain proteins taking parts in regulation of cell cycle, proliferation and cell differentiation and communication. Usually, a combination of several factors leads to carcinogenesis. Out of known carcinogenic factors, mainly the life style, in particular dietary habits and smoking, are important. The quality and quantity of food also influence carcinogenesis. Foodstuffs may contain carcinogenic compounds but also compounds with anticarcinogenic effects. The number of carcinogenic compounds that may occur in food is high but, fortunately, their concentrations are very low. A synergism of carcinogenic effects often occurs. Natural carcinogens in foodstuffs, carcinogenic contaminants originating from metabolic and microbial processess and mycotoxins are described in this paper. Acceptable intakes of carcinogens and their carcinogenic potential are mentioned if available.