Gastro-intestinal nematode infections are responsible for important economic losses in sheep and goat livestock. The blood feeding nematode parasite Haemonchus contortus is the most pathogenic of the small ruminant's nematodes parasites. Anthelmintics are questioned, due to the emergence of resistant isolates and the development alternative control methods is urgently needed. A better understanding of the relationship between host and pathogen could allow the finding of a new way to control parasite infestation. P-glycoproteins (Pgps) are membrane pumps creating efflux of toxic substances. They might have a role in the efflux of the host toxic products. Thus, this work enabled to identify ten Pgps genes in H .contortus. The analysis of the expression of these genes shows a differential kinetics of expression during the nematode development of two of the ten genes (Hco-pgp-la and Hco-pgp-3). These Pgps present an over-expression in parasitic stages compared with free-living stages. Moreover, the comparison of the expression of these genes in the free living stages (egg and Ll) of nematodes in contact or not with the host's products (25 ,000 granulocytes, mucus and abomasums) showed that the expression of Hco-pgp-la remains stable after stimulation while the expression of Hco-pgp-3 is decreased. These results provide a basis for determining the role of Pgps in the detoxification of nematodes parasites in their hosts. This could allow us to identify new vaccine and/or therapeutic targets.