Computer diskettes can be colonized by saprophytic fungi, especially in the humid tropics. Fungi of the generaAlternaria, Aspergillus, Epicoccum, Paecilomyces, Penicillium, andTrichoderma were observed on diskettes from several tropical countries. Common saprophytic fungi from Minnesota colonized clean standard and high density diskettes in growth chambers, indicating that fungal contamination could occur wherever temperature and humidity were adequate.Fusarium species infested diskettes buried in garden soil in Minnesota. Audiotapes, videotapes, and computer magnetic tapes chemically resemble diskettes and also can be colonized by fungi, as can photographic film. The Mylar core of these magnetic media did not support the growth ofPenicillium glabrum, the most aggressive fungus in diskette inoculation studies. However, growth of several fungal species was enhanced when the common plasticizer, lecithin, was added in powdered form to nutrient agar, suggesting that this ingredient of the diskettes may be metabolized by the fungi.