The diagnosis of ruminant theileriosis in Turkey is based on microscopical examination of thin blood and lymph smears, serology, traditional staining methods of the salivary glands of ticks and molecular techniques. Although some investigators reported that T. mutans was found in cattle with microscopic examination (7.4%-36.7%) and experimental study, they did not detect this parasite using molecular techniques. On the other hand, the prevalence of T. buffeli/orientalis was found to differ between 0.9% and 13.6% using molecular techniques in different regions of Turkey. Tropical theileriosis caused by T. annulata is widespread, and constitutes a major health and management problem in cattle in Turkey. The economic losses resulting from the tropical theileriosis were estimated to be US $598,000, $133,000 and $130,000 in the endemic stable zones of Turkey. Microscopic prevalence of T. annulata has been reported to be between 0% and 60.5% in different parts of Turkey. The serologic prevalence of T. annulata was found to differ between 1.8% and 91.4% by IFAT. In subsequent studies, the prevalence of this parasite was found to differ between 15.4% and 61.2% by molecular techniques. Clinical cases of ovine theileriosis have not been documented in Turkey. The prevalence of T. ovis/recondita was found to differ between 0% and 41.3% by microscopic examination of thin blood smears and its seroprevalence was found to be between 8.2% and 63.2% by IFAT. This parasite has also been reported to be present between 41.8% and 67.7% by molecular techniques.