A review of the natural history literature of small mammal feeding habits, based on many for-tuitous field observations, some analysis of stomach contents, and a few feeding experiments, showsthat diverse animals feed on similarly diverse fungi. The interdependence of animals and fungi hasevolved to a high degree in some cases, e.g., the loss of alternative spore dispersal mechanisms bysome fungi and the strong reliance of some mammals on fungi as a primary food. Consequently,adaptation for mycophagy and the effects on mycophagy of habitat, fungal toxicity, and the foodvalue of fungi have implications in the interpretation of ecosystem structure and function.