Lesioning and gene expression studies have implicated the insect mushroom bodies as centers for olfactory processing and associative learning and memory mediated by a cAMP signaling pathway. However, several lines of evidence suggest that the primary role of the mushroom bodies may be a more general computation applicable to functions outside of olfaction and associative learning. First, comparative studies have described intrinsic circuitry, inputs and outputs that are not compatible with the concept of the mushroom bodies as dedicated olfactory learning centers. Second, the mushroom bodies are necessary for a large number of behaviors that are difficult to reconcile with a primary role in olfactory learning and memory. Third, recent anatomical and physiological studies suggest that mushroom bodies are not likely to play a role in odor identification, as might be predicted for a structure involved in the formation of odor-specific associative memories. Finally, the mushroom body circuit shares many features with vertebrate cerebellum-like structures, which are involved in many types of behaviors but serve an underlying role as adaptive filters for separating predictable from novel sensory input. Taken together, this data suggests that the role of insect mushroom bodies in olfactory learning is only a part of the entire picture of insect mushroom body function. Broadening the scope of experimental studies of insect mushroom bodies, perhaps by incorporating lessons learned from vertebrate cerebellum-like structures, will provide a more complete understanding of the behavioral significance of these insect higher brain centers.