Technical Abstract: Predators and parasitoids move through the landscape at a wide range of rates and over a broad range of spatial scales. Understanding the dispersal characteristics of such 'beneficials' is of crucial importance for classical, augmentative, inundative and conservation biological control. It is a key practice, following the release of 'classical' (exotic) and augmentative (indigenous) biological control agents, to assess whether they have become successfully established, and also to what extent the agent has spread from the release points. It is important in conservation biological control to understand the role that natural enemy movements play in the improvement of pest control achieved through the provision of pollen, nectar, shelter and/or alternative prey/hosts. Other aspects of predator and parasitoid movement pertinent to biological control are the role refugia play in influencing, via natural enemy movements, control of pest population numbers. In these areas and others, some form of marking and/or tracking of insect predators and parasitoids is usually required so that movements can be studied. This special issue considers the usefulness and limitations of marking and tracking techniques, through up-to-date reviews written by an international team of researchers who are actively involved in the study of predator and parasitoid ecology.