The collection of large numbers of nematodes from amphibians (Telmatobius sp.) and fish Orestias luteus Valenciennes, 1839 Arequipa, Puno, and Titicaca Lake in South Peru has made possible the revision of one species and the description of our new species: Hedruris orestiae Moniez, 1889 is re-described; Hedruris moniezi sp. n., Falcaustra condorcanquii sp. n., Falcaustra pumacahuai sp. and Falcaustra tiahuanaquensis sp. n. are described.