The olfactory response of maggots (the larvae of cyclorrhaphous flies) and its neuroanatomical basis have been a subject for scientific investigation since the 17th century, preoccupying both fundamental and applied scientists. Despite its apparently arcane nature, the subject raises a series of major neurobiological problems, in particular, the relationship between the number of odours that can be detected and the apparently simple systems of detection and processing available to larvae. Molecular biological techniques in both neuroanatomy and cell biology have made it possible to begin to resolve some of these problems, if data from a wide range of studies are integrated. Four sectors of research on a large number of species are reviewed: the behaviour involved in the olfactory response, the wide range of odours that can be detected, the neuroanatomical basis of olfaction in cyclorrhaphous larvae and the number of receptors involved in detecting these odours. Finally, a neuroanatomical model of olfactory processing is presented, together with perspectives for future research, emphasising the importance of studying the ecology of the species under investigation.