Augmentative biological control uses mass-reared natural enemies for releases in large numbers to reduce pest populations. Augmentative biocontrol is increasingly applied worldwide in many different crops. It is a cornerstone of integrated pest management (IPM) programmes and plays a key sustainability-determining role in IPM. This chapter describes the scale of augmentative biological control and where this type of biocontrol is applied. The chapter describes the natural enemies commercially available and gives information on their mass production. The chapter discusses the important role of biocontrol in IPM programmes, and its practical use in very different agricultural production systems. Finally, the chapter presents the advantages and disadvantages of this control method, and looks ahead to future research trends in this area.