In Uruguay, gastrointestinal nematodes (GINs) are one of the major thread to the ovine production systems. The continuous use of chemical drugs as the main control measure has lead to the development of anthelminticresistance (AR). Resistance to bencimidazolewas first diagnosed in 1990. After that, a cross‐sectional study conducted during 1994‐1995 demonstrated that resistance to bencimidazoleand levamisolewas highly prevalent and spread among sheep farms , all over the country. The main nematode species involved in the resistance were Haemonchuscontortusand Trichostrongyluscolubriformis. Thereafter, different laboratory reports indicated that the prevalence of AR has increased (Table 1) . The objective of this work is to present AR results from a retrospective study conducted on 36 sheep farms, in Uruguay.