Our studies have focused on the examination of fungi infesting artworks and artifacts on paper. We have been concerned primarily with the mechanisms of deterioration by fungi and the role played by the composition of the substrates upon which the fungi grow. Several examples illustrate these relationships: (1) infestations that occurred after exposure to periodic floods (18th century Tilghman documents); (2) exposure to water spills (19th century watercolor and ink drawings); and (3) growth occurring in the microclimate of framed artworks exposed to fluctuating relative humidity (18th and 20th century panel portraits). Part of our investigation was aimed at the identification and numeration of the vast mycoflora that has been encountered on paper-based collections. Several groups of fungi appear to be common on the materials we examined. While Deuteromycetes (Fungi Imperfecti) dominate, we often find members of the Zygomycetes (bread molds), Ascomycetes (sac fungi) and Saccharomycetales (yeasts). Their growth is often linked to the materials upon which artwork and archival documents are rendered and the environment to which these works are exposed throughout their life. Moreover, fungus growth is often enhanced by the addition of artists' pigments and the great variety of materials, such as varnishes, glazes, and additives, applied later in the life of the artwork. The impact of the environment, specifically the time of the collections' exposure to moisture, greatly enhances both the number of species and the abundance of fungal growth. This report reviews the current status of our understanding of these fungus-substrate parameters, discusses their impact upon the preservation collections, and concludes by offering a number of suggestions to consider for future practices when choosing methods of conservation.