This book attempts to provide an overview of the food contaminant, aflatoxin, with adverse effects on human and animal health. Aflatoxins are one of the food contaminants of greatest concern in food safety and was identified decades back. Still, it is prevailing today not only in developing countries but also in developed countries. The first reason is that aflatoxin is a a toxin produced by Aspergillus species (mainly Aspergillus flavus and Aspergillus parasiticus), the fungus with one of the most diverse range of substratum adaptability for growth and is ubiquitously found in a variety of food commodities such as, cereals, nuts, spices and herbs. The second reason is that the main route of exposure is through the diet, and this toxin can cause disease, even if the meat of an animal is consumed, which was fed on aflatoxin contaminated feed. Depending upon the type of exposure, humans can develop acute aflatoxicosis or chronic alfatoxicosis, which is essentially long-term aflatoxin exposure and is linked to the development of hepatocellular carcinoma. On the other hand, acute aflatoxicosis is characterized by one time high dose of aflatoxin contaminated diet, causing hemorrhagic necrosis of the liver, bile duct proliferation, edema and lethargy, which subsequently damages the liver and further leads to death. In this book we have discussed the topics aflatoxin biosynthesis, aflatoxin contamination in foods and feeds, aflatoxicosis in human and animals. It is an attempt to understand and manage the occurrence of human and animal exposure to aflatoxin.