ELISA indirect tests revealed the presence of antibodies to Bovine Leukosis Virus (BLV) in 12.5 ±± 3.3% (n= 47/377) of serum samples from 8 herds of extensively reared dual purpose cattle (n=342 female, 35 male) in Obenteni (Gran Pajonal, Ucayali, Perú). Based on the 89% sensibility ofthis ELISA test, however, the prevalence ofBLV in this sample is 2.55 ++ 1.59%. Although ali ofthe herds tested were infected to varying degrees, and the highest frequencies of antibodies were found in adult animals (cows=l2.9%, bulls=28.6%), the overall incidence of BLV reactors is low compared to other areas of the Peruvian tropics, such as Pucallpa. For this reason, controls should be established to prevent the introduction of BLV infected animals to this potentially important cattle producing area.