The diagnosis equine granulocytic Ehrlichiosis was made on a one year old Friesen mare and on two 1 8-year old mares by blood smears due to the rnorula in bonds. The etiologic diagnosis Anaplasmo phagocyfophilum infection was found using FAT and the evidence of the genomic DNA was confirmed by nested PCR. Ixodes ricinus was found on the surface of the skin in all patients. The symptoms were depression (3/3), partial loss of appetite (3/3), edema on the lower chest (1 /3), fever (1 /3), icterus (2/3), pale mucous membranes (1 /3), tachycardia (1/3), abnormal lung sounds (2/3), petechia, ecchymoses (2/3), and brown ("like a coffee") urine (1/3). The clinical pathological data were ancemia (2/3), increased erythrocyte sedimentation rate (2/3), leukocytosis (1/3), thrombocytopenia (3/3), hypoollauminemia (1/3), fibrinogenemic (2/3), azotemia (1/3) and prolonged prothrombin and activated partial thromboplastin time (1/3). Complications appeared in the young mare such as acute renal failure, pneumonia and laminitis. Oxytetracycline was used as an antibiotic of choice with a dosage of 7 mg/kg b.w. bid intravenously until the thrombocytes were in normal range. The older mares have been discharged after seven days. The young mare has been looked after providing intensive medical care so she could be released after seven months despite suffering on a fracture of the iliac bone. Seroepidemiologic surveys of horses where the patients came from have shown between 26 and 33% prevalence.