In previous studies, two bovine Sarcocystis species including Sarcocystis cruzi and Sarcocystis hominis have been reported in cattle of Iran. Based on our knowledge, there is no study about identification of Sarcocystis hirsuta in the country. A total of 100 cattle, 63 males and 37 females with different ages were examined for Sarcocystis hirsuta cysts. At first for macroscopic sarcocysts, tongue, esophagus, diaphragm, and heart were carefully inspected by naked eye examination. For light microscopic studies, tissue samples from oesophagus and diaphragm were taken and processed for routine haematoxylin and eosin staining. Based on light microscopic characteristics of sarcocysts, the samples from paraffin blocks were selected and processed for transmission electron microscopic observation.In light microscopy, 16 out of 100 cattle (16%) had thick and smooth walled sarcocysts identified as S. hirsuta. In transmission electron micrographs of them, the villar protrusions constricted at the base, expanded laterally in the mid-region and tapered at the end. The end portion of the villar protrusions was bent at an angle of 45– 90° to the sarcocyst surface. The villar core contained numerous microfilaments and electron-dense granules. Based on histopathological and ultrastructural features of the cysts, we identified them as Sarcocystis hirsuta.

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