Arbuscular mycorrhizas (AM) are one of the most widespread and common type of symbiotic associations. Lycopodium paniculatum and Equisetum bogotense are two important species of seedless vascular plants in a Valdivian temperate forest of Patagonia, Argentina. The mycorrhizal status of these species is completely unknown, as it is for most lycophytes and monilophytes in Argentina, where information on symbiotic interactions in these plants is scarce. In this study, typical AM structures were observed in sporophytes of L. paniculatum and E. bogotense. The percentage of root length colonized by AM fungi ranged from 0 to 50% in the first species and from 0 to 22.5% in E. bogotense. Both species were facultative mycorrhizal and it was observed that the habitat and substrate seem to play an important role in determining the colonization intensity. The morphological AM colonization pattern was considered an Intermediate-type. Dark septate fungi, characterized by septate hyphae and microsclerotia, were also present within the roots of L. paniculatum and E. bogotense.