The current distribution and host range of the Sclerotiniaceae indicate that the family originated in the Northern Hemisphere. The ancestors were possibly present on earth during the Tertiary period when, in most northern areas, environmental conditions were wet, warm and uniform until the approach of the Pleistocene epoch. It seems from present-day host–pathogen relationships that some ancient groups of plants and a variety of angiosperms were hosts. The teleomorph of early genera was well adapted to wet conditions, with ascospores the only dispersive spore and microconidia probably serving a spermatial function. Macroconidia were probably later evolutionary developments associated with colonization of habitats drier than the original one. The onset of the Pleistocene Ice Age would have exerted considerable environmental pressures on early genera resulting in selection of adaptations which enabled survival of the gradually changing conditions, particularly sub-zero temperatures and unavailability of hosts during the harsh winter months. The major adaptations in the Sclerotiniaceae have been a range of multihyphal, reserve-rich resting structures which survive harsh environmental conditions and provide nutrients and protection for the teleomorphs, which are highly sensitive to cold and desiccation. The resting structures are useful indicators of phylogenetic relations within the family. Information on stromata and sclerotia of the Sclerotiniaceae is reviewed and then used to discuss evolution of these structures. The first type of resting structure to evolve was probably an indeterminate stroma which developed by branching and interweaving of infection hyphae within host tissues. Several, better differentiated forms were produced with their morphology related to type of host and tissue infected and to characteristics of the pathogens. The different stromata could have evolved along a common pathway or independently. The general anatomical similarity of the various structures could be accounted for because of the limited structural forms that can be produced by interweaving of filamentous hyphae. It seems that sclerotia may have developed from hyphal tissue which had the ability to produce sclerotia when the climate was cold and wet, and macroconidia when conditions were warmer and drier. Two main types of sclerotia are distinguished, tuberoid sclerotia and plano-convex sclerotia. The literature relating to the morphology and ontogeny of macroconidia is reviewed and used for speculation on the effects of environmental conditions on evolution of macroconidia, the origin of macroconidial anamorphs and stages in the evolution of botrytoid spores. It is concluded that in the Sclerotiniaceae there are at least two main pathways along which resting structures have evolved, one leading to a variety of stromata and the other to two types of sclerotia. Sclerotia predated macroconidia and both anamorphs could have originated from common generative tissue.