BACKGROUND: The Cryptococcus spp is currently composed of encapsulated yeasts of cosmopolitan distribution, including the etiological agents of cryptococcosis. The fungus are found mainly in substrates of animal and plant origin. Human infection occurs through inhalation of spores present in the environment. METHODS: Eighty-four swab collections were performed on dust found on books in three libraries in the city of Cuiabá, state of Mato Grosso, Brazil. The material was seeded in Sabouraud agar and then observed for characteristics compatible with colonies with a creamy to mucous aspect; the material was then isolated in birdseed (Niger) agar and cultivated at a temperature of 37°C for 5 to 7 days. Identification of isolated colonies was performed by microscopic observation in fresh preparations dyed with India ink, additional tests performed on CGB (L-canavanine glycine bromothymol blue), urea broth, and carbohydrate assimilation tests (auxanogram). RESULTS: Of the 84 samples collected from book dust, 18 (21.4%) were positive for Cryptococcus spp totalizing 41 UFC's. The most frequently isolated species was C. gattii 15 (36.6%); followed by C. terreus, 12 (29.3%); C. luteolus 4 (9.8%); C. neoformans, and C. uniguttulatus 3 (7.3%), and C. albidus and C. humiculus with 2 (4.6%) of the isolates. CONCLUSION: The high biodiversity of the yeasts of the Cryptococcus genus, isolated from different environmental sources in urban areas of Brazil suggests the possibility of individuals whose immune systems have been compromised or even healthy individuals coming into sources of fungal propagules on a daily bases throughout their lives. This study demonstrates the acquisition possible of cryptococcosis infection from dust in libraries.