Ochratoxin is a kind of secondary metabolite produced by Aspergillus and Penicillium. It mainly contains Ochartoxin A (OTA), Ochratoxin B (OTB), Ochratoxin C (OTC), 4-hydroxyochratoxin A and Otα, and among which OTA has the strongest toxicity. Ochratoxin exists widely in a variety of food products, such as wheat, corn, soybean, oats, barley, coffee beans, meat and cheese. Ochratoxin carries potential health-associated risks, and it has caused wide public concern in recent years. This book has been written with the aim of helping investigators in this field by providing information about the production, isolation, purification and the toxic mechanism of OTA. This book consists of six chapters. Section I introduces the discovery and the classification of ochratoxin. Section II describes the biosynthesis and metabolism of OTA and the ways of OTA control. Section III deals with detection methods of OTA. In the last three sections, toxicities of OTA are the emphasis of this book. The kidney and the liver are the main target organs of OTA. Nephrotoxicity, hepatotoxicity and other toxicities, such as intestinal metabolism toxicity and reproductive toxicity, are stated in section IV, V and VI, respectively. In these sections, methods of both traditional toxicology and molecular toxicology evaluation are applied to explore OTA-induced toxicity. Traditional toxicology describes the changes of OTA-induced toxicology indexes, containing blood biochemistry indexes and pathological parameters, and the molecular toxicology mainly focuses on the signaling pathways of its toxicity. A combinatorial approach encompassing miRNA, mRNA, and proteomic profiling and bioinformatics methods have also been used to study the molecule mechanisms.