Prior to the discovery of DDT, botanical insecticides – those prepared directly from plants – represented the majority of pest control products in the farmer's arsenal. Then with the spectacular growth of the agrochemical industry, botanicals were all but trivialized in the pest management marketplace. Research in the field of natural products chemistry indicates that terrestrial plants represent a vast, largely untapped resource with respect to novel chemistry, much of which is presumed to have an ecological function. Many scientists have used these facts to justify the ongoing search for new insecticides derived from plants, even though the actual number of commercially viable botanical insecticides is very small. In this chapter we review the current status of botanical insecticides, their mechanisms of action against pest insects, and the challenges to developing and commercializing new botanical insecticides.