This study was conducted to determine theinfection rate of Sarcocystis species in sheep in Assiut. A total of 100 slaughtered sheep examined for Sarcocystis, no macroscopic cysts were observed, 93% (93/100) were positive by microscopical examination and 28% (28/100) were positive by using Agar gel diffusion test.Theinfection rate of Sarcocystis had very high significant differences between microscopic examination and Agar gel diffusion test. High statistical significant effect was found on the infection rate of Sarcocystis in different examined muscles of sheep. The highest infection rate was recorded in oesophagus (71%), followed by diaphragm (65%), tongue (58%), skeletal muscles (53%) and heart muscles (43%). The infection rate of Sarcocystis in males was 95.2% (40/42) while in females were 91.4% (53/58) by microscopical examination. Higher infection rate of Sarcocystis were detected in sheep 6 months - 2 years age 95% (38/40) than that of sheep between 2-4 years old 92.7% (38/41) and those equal or older than 4 years 89.5% (17/19). No significant difference between infection and age groups or sex of animals was observed. The use of transmission electron microscope (TEM) allowed the identification of S. tenella and S. arieticanis in sheep in Assiut. Examination of S. tenella cyst wall with TEM showed palisade-like villar protrusions while, examination of S. arieticanis cyst wall showed hair-like villar protrusions parallel to cyst wall.