The present study was planned to demonstrate the clinical findings, post mortem lesions of BEF and to study theeffect of the disease on blood picture including red blood cells, hemoglobin concentrations, total and differentialleucocyte counts as well as total serum protein, serum albumin, glucose, alkaline phosphatase in addition to Kidneyfunction tests as creatinine and urea and finally biochemical parameters which include the estimation of seruminorganic phosphorus, calcium and magnesium. The study was conducted on 30 Friesian dairy cows from privatefarm at El-dalangat, Behera Governorate. 10 cows were clinically healthy and kept as control while 20 cows werediagnosed clinically and confirmed by immunofluorescent (IF) test as bovine ephemeral fever. The results showedclinical signs in the form of fever 40-41.5° C with waves of muscle shivering, fall in milk production andaccelerated heart and respiratory rates, depression, anorexia, ruminal atony, salivation, a generalized stiffness or ashifting lameness of diseased cows, recumbency occurring in Many animals for 12-24 hours with sever tympanybut are able to rise if sufficiently stimulated. Recovery begins after sever clinical signs disappear and earlyimprovement that fever disappears in most cattle. A range of complications occurred in five cases. Death occursuddenly in one case during febrile phase. Recumbency persist for three weeks in (2) cases and recovery from thelonger-term recumbence complete after three weeks and abortion occur in (2) cases in a late stage of pregnancy(eighth month of pregnancy). The observed post mortum lesions were pulmonary emphysema, alveolar collapse,exudate found in bronchioles and bronchioles became completely occluded by exudate, fibrin-rich exudate inpleura, pericardial and in the joint capsules and Lymphadenitis. A significant decrease (p<0.01) in RBCs count andhemoglobin concentration in cows suffering from bovine ephemeral fever. Also, there were marked leukocytosis,neutrophilia and lymphopenia, but Monocytes, eosinophils and basophil percentage did not seem to be influenced,In addition, total proteins, albumin, globulin, glucose, Inorganic phosphorus, calcium and magnesium showedsignificant decrease (p<0.05), while alkaline phosphatase activity, urea and creatinine increased significantly(p<0.01) in these diseased cows. It can be concluded that ephemeral fever in cattle has a range of hematologicaland biochemical changes in blood which are characteristic of an inflammatory response, These information willhelp to plane a strategy to decrease losses of the disease through effective treatment specially hypocalcaemia.