The present work aims to estimate the seroprevalence of Bovine Enzootic Leukosis - LEB and to identify the risk factors associated with seroreactivity for infection by the LEB virus, in cattle from herds raised in the Teresina Microregion, in the State of Piaui, Brazil. 420 blood samples were examined in 14 municipalities belonging to the microregion, the technique used for the research was Immunodiffusion in Agar Gel (IDGA). There was a prevalence rate of 19.52% (82/420) of seroreagent animals, with the occurrence of at least one animal positive for LEB in each herd evaluated. The results show that prevention and control measures are necessary for better surveillance of herds.