A new nivicolous species of Perichaena is described from the Andes in Argentina. The most conspicuous characteristics of Perichaena megaspora are the large spores and their ornamentation in the form of flattened warts. The 16-21 μm diam spores make the new species unique in the genus in which all other species have spores rarely reaching 15 μm diam. Twenty-two collections were found in the field during two consecutive years at 10 localities in Mendoza province Argentina, including one collection isolated from a moist chamber culture of ground litter. The new species was examined under stereomicroscope, light microscope and scanning electron microscope and micrographs of relevant details are included.