Aflatoxins are toxic metabolites produced mainly by Aspergillus flavus and Aspergillus parasiticus and naturally occurring contaminants of food. Aflatoxin poisoning is a recurrent public health problem. Acute exposure to high levels of aflatoxins causes aflatoxicosis and chronic exposure to low levels of aflatoxins is one of the major risk factors in the etiology of carcinoma in several regions of the world including India. More than 5 billion people in developing countries are at risk of chronic exposure to naturally occurring aflatoxins. The International Agency for Research on Cancer classifies aflatoxin B1 within Class 1 of human carcinogens. Aflatoxin B1 is the most toxic mutagenic, genotoxic and carcinogenic among the known aflatoxins. We have evaluated systematically and presented data in this book whether chronic exposure to low doses of aflatoxin B1 has any significant effect in adult male Wistar rats. This book also provides valuable information on effect of exposure toaflatoxin B1 during embryonic period on reproduction of male progeny.