Heart rot fungi cause substantial economic loss in many forests, but their ecological roles in altering the speed or direction of succession are frequently overlooked. As heart rot induces trees to die standing or, more commonly, by bole breakage, the fungi that cause heart rot can be viewed as both pathogens and agents of disturbance. Many forests that do not experience frequent, large-scale disturbance, such as those where fire is rare, are composed of old trees. Heart rot fungi are abundant in these old forests and are important ecologically as disturbance agents by initiating and sustaining canopy gaps. Heart rot fungi also have profound influence on numerous structures and processes such as nutrient cycling, vegetation composition, and wildlife habitat. This paper uses the western hemlock/Sitka spruce (Tsuga heterophylla/Picea sitchensis) temperate rain forest of southeast Alaska to explore ecological consequences of heart rot, including the role of heart rot fungi in canopy gap formation.