Only one study of T. equi prevalence has previously been performed in Mexico. In that study, 248 horse serum samples were analyzed by IFAT . The aimof this studywas to determine the prevalence and assess the current epidemiological status of T. equi among horses in the state of Jalisco, Mexico, which has the highest equine population in westernMexico. In our country, this study is the first to use amolecular diagnostic method (nested PCR [nPCR]) to obtain information regarding the prevalence of T. equi and provides a basis for future studies assessing the genetic diversity of this pathogen.