A contribution to the study of the gametophyte's morphology and development of some species of Thelypteris Schmidel (Thelypteridaceae). The development and morphology of the sexual phase of five species of the Thelypteridaceae family is described and compared. Spores were sown in Thompson medium with agar, germination occurred after 11 days; all spores of the species studied are monolete, ellipsoid with a pleated perine, brown to dark brown; the germination pattern is Vittaria type and the prothallial development is Aspidium type. Gametangia are of the common type of the leptosporangiate ferns. Sporophytes in Thelypteris reptans var. reptans and T. tetragona appear 90–285 days after sowing; T. dissimulans, T. piedrensis and T. oviedoae did not develop any sporophytes. The sexual phase of these species has many morphological characteristics in common with species of the Old and New Worlds.