ABSTRACT:The Khuzestan province in south-western Iran is the centre of Persian Arab horse breeding and training. The present study was aimed at determining the prevalence of Theileria equi in the equids of this province. A total of 165 blood samples from healthy Persian Arab horses from twenty four stables were examined for the presence of T. equi infection using molecular methods. For detection of T. equi, primers targeting the 18SrRNA gene were selected. The PCR method gave 47 (28.5%) positive results. Age (P = 0.68), sex (P = 0.88), contact with cattle (P = 0.26) and type of activity (P = 0.06) were not determined as risk factors for T. equi infection in this study. However, there was a significant geographical variation in the prevalence of T. equi infection ranging from 8.3% (2/24) in Shushtar to 55.6% (10/18) in Ramhormoz (CI, 2.46-76.82) (P = 0.003). In conclusion, equine theileriosis has the potential of posing a significant problem for Iran's Persian Arab horse industry and should remain a major concern to the horse community and regulatory agencies.