Insects are major pests for crops. Enormous losses occur when they attack various plant parts, often transmitting various diseases in the process. Even after harvest, insects attack stored plant or animal foods. Insects are also vectors of various animal and human diseases. Over the past decade or so, there has been a shift from the sole use of chemical control towards integrated control which employs other methods along with chemical control. The reasons for this include non-specificity of chemical insecticides leading to the destruction of pests as well as their natural predators, resistance to chemical insecticides, and concern for the environment and human health, since the insecticides enter drinking water from soil and are potentially toxic or carcinogenic. Furthermore, the cost of chemical insecticides manufactured from petroleum hydrocarbon will increase with increase in cost of petroleum hydrocarbon. This chapter describes alternatives to chemical insecticides, biological control of insects, desirable properties in organisms to be used for biological control, Bacillus thuringiensis insecticidal toxin, production of biological insecticides, submerged fermentations, surface culture, in vivo culture, bioassay of biological insecticides, formulation and use of bioinsecticides, safety testing and development of new bioinsecticides.