Mycotoxins are secondary fungal metabolites, toxic to humans and animals. Toxigenic fungi often grow on edible plants, thereby contaminating food and feed. The most common mycotoxins are produced by the genera Fusarium, Aspergillus and Penicillium. While Fusarium species are plant pathogens producing mycotoxins (trichothecenes, fumonisins and zearalenone), before or after harvest, species of the genera Aspergillus and Penicillium are frequent contaminants of food during processing and storage. The most toxic mycotoxins produced by the genera Penicillium and Aspergillus are aflatoxins and ochratoxin A. Their occurrence is not only associated with plant commodities, but they are also found in products of animal origin. Plants, as living organisms, can alter the chemical structure of mycotoxins as part of their defence against xenobiotics. The extractable conjugated or non-extractable bound mycotoxins formed remain present in the plant tissue, but are currently neither routinely screened for in food nor regulated by the legislation, for which reason they may be considered masked. Fusarium mycotoxins (deoxynivalenol, zearalenone, fumonisins, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin, fusaric acid) are prone to metabolisation or binding by plants, though the transformation of other mycotoxins by plants (ochratoxin A, patulin, destruxins) has also been described. A potential threat to consumer safety can occur from these substances, particularly due to the possible hydrolysis of masked mycotoxins back to their toxic parents during mammalian digestion. The occurrence of masked mycotoxins in food and analytical aspects for their determination and toxicology must be studied in detail. This review focuses on the types and occurrence of various kinds of mycotoxins in food and feed associated with risks to humans and livestock as well as their significance.