Muscodor crispans (isolate B-23) is described as a new species of Muscodor. It is an anamorphic sterilia endophytic fungus residing within the stem tissues of Ananas ananassoides, a wild pineapple in the Bolivian Amazon Basin. This strain is characterized by the production of a pinkish felt-like mycelium on potato dextrose agar (PDA) and other media under lighted conditions, but developing a whitish mycelium in the dark. The fungus produces no fruiting structures or spores of any kind when incubated on multiple synthetic or natural media. On PDA and other common laboratory media, its hyphae develop into regular undulating patterns and associated with them are cauliflower-like structures (3.5-14 μm). Analysis of the volatile organic compounds it produces in culture by GC/MS showed that M. crispans primarily produces a number of esters, alcohols, and small molecular weight acids, but no naphthalene or azulene derivatives as other members of this genus. The volatiles possess antibiotic properties making this organism potentially useful in a number of situations. A molecular genetic analysis of the ITS1, 5.8S rDNA, and ITS2 regions showed 100% similarity to Muscodor albus. Muscodor albus, M. roseus and M. vitigenus are each genetically related to xylariaceous taxa by virtue of ca. 95% sequence similarity to this group. Justification for the designation of a new species is primarily based on the novel phenotypic characters of isolate B-23 including its peculiar hyphal growth patterns (undulating hyphae), its reddish pigment production in the light, the odd cauliflower-like structures associated with its hyphae, and its unusual gaseous products. In spite of its 100% genetic similarity to the rDNA regions of M. albus, this organism is considered distinct because of the number and kind of its unusual phenotypic characteristics. The rDNA sequence data obtained represents well less than 1% of the total DNA of a fungus.