The aim of this study was to characterize the worm burdens acquired by pastured animals in the Pyrenees (Spain). Distribution, species of gastro‑intestinal nematodes and relationships among them at different grazing intervals were studied. Prevalence of parasitism was very high. Almost 100% of the animals had gastrointestinal parasites. At necropsy, it was found Ostertagia osteragi, Ostertagia lyrata, Trichostrongylus axei, Cooperia oncophora, Capillaria bovis, Nematodirus helvetianus, Trichostrongylus longispicularis, Trichuris spp., Chabertia ovina and Oesophagostomum radiatum. In addition, Teladorsagia circumcincta was also found in one group. Ostertagia osteragi was the most frequent species observed, followed by Cooperia oncophora and Trichostrongylus axei, being these 3 species the most often found together. A big despropotion among abomasal, small and large intestinal worm burdens was observed, especially in the animals that only grazed one month. Animals on pasture for longer periods had more similar worn burdens between abomasum and small intestine, although abomasal populations were always the highest. Worm burdens in the study were low, but associated to subclinical parasitism responsible of productive losses in the animals.