This investigation was developed at the sabanas of the deparment of Casanare, Colombia, between june/2006 and april/2007, with the objective to clas- sify the parasite population that affect gastrointesti- nal and pulmonary system. The equine faecal sam- ples were taken of four towns of Casanare: Aguazul, Paz de Ariporo, Mani and El Yopal. Ten fresh sam- ples were taken from each town, directly on pasture and completely radomized. The faecal samples were analyzed by MacMasters technique that showed gastrointestinal nematodes eggs of type Strongylido spp., Strongyloide spp., Triodonthoforus spp., Ha- bronema spp., and Oxyuris spp.. By Coprocultives the parasite genere found were: Small strongylus (86.2%), Strongylus vulgaris (6.2%), Strongylus eden- tatus (3.6%), Strongylus equinus (2.8%), Strongylio- des westeri (1.1%) and Trichostrongylus axei (0.20%), and by Baermanns technique it was not found Dyc- tiocaulus spp.