Biological Control of Insect Pests is a book that deals with the most relevant biological control agents and their application to important agriculturally insect pests. A detailed revision of bacteria, fungi, viruses, and predators as control agents is offered through their taxonomic classification, mode of action, activity spectrum, killing abilities, genetics, and suitable application according host range. In addition some particular characteristics of each one of them are highlighted in order to distinguish from those organisms without entomopathogenic properties. It also includes interesting descriptions about important pests in agricultural crops that cause economic losses to producers, and how biological control has offered a successful alternative to control lepidopterans, which are considered the first insect pests attacked by this technology, and coleopterans which are one of the latest insect pests to be controlled as a result of expanded activity spectrum found through scientific research. An important aspect of this book is the inclusion of biotechnological tools in the development of biological control agents. The use of the traditional and modern biotechnology to develop new strategies to control insect pests is presented in a broad sense. From the development of strategies that make use of biodegradable compounds to develop environmentally-friendly bioinsecticides to the application of molecular tools to improve control agents effectiveness against insect pests. Up dated lists of products based on entomopathogenic organisms are also included with briefs explanations of their use and application. Molecular biology techniques used for gene identification, genetic recombination, mutation, formation of truncated or modified proteins known as chimeric proteins, to enhance agents’ toxic activity are explained in a scientific but clear manner. The implications and interactions of the biological control application in the environment, posed by the risks of the introduction of exotic enemies, are clearly analyzed to understand how the nets of interactions among organisms impact towards non target insects, flora, fauna, and human beings.