This book evaluates the risks to human health and the environment posed by the use of Bacillus thuringiensis (Bt) as a microbial agent for pest control. Products containing various Bt subspecies are increasingly used worldwide to control the larvae of several insect pests that threaten major agricultural crops and forests. Bt products are also being used to control the insect vectors of malaria, onchocerciasis, and other diseases of major public health importance. The bacterium is also a key source of genes for transgenic expression to provide pest resistance in plants and microorganisms.