During the period from June 2010 to May 2011, the present study was coducted on 150 cross bred cattle , their ages ranges from 1-5 years. These animals belonged to some private farms in different localities in Ismailia Governorate. The clinical examination showed 48 suspected cases which have the signs of theileria infection. Laboratory parasitological examination confirmed that infection of 45 animals infected with Theileria annulata (30.0 %) where high body temperature (40 - 41º C ), enlargement of superficial lymph nodes , anorexia, congestion of mucous membranes and increased respiratory rates were noticed. In advanced cases of the disease, signs of anaemia, general weakness were present with various degrees in addition to presence of ticks on animal body. The study revealed that the higher rate of infection was in Autumn (47.73%) followed by Summer (42.50%), Spring (11.11%) and Winter (10.0%). Concerning the prevalence of Theileria annulata infection , it was found that Fayied region was the higher rate of incidence (32.43 %) followed by Qantara (31.11%) and El-Tal El-Kebeer (27.94%). The study showed that presence of microcytic hypochromic anaemia represented by high significant decrease for total erythrocytic count, haemoglobin concentration and packed cell volume. On contrary presence of high significant increase in neutrophils and esinophils and significant increase in basophil , in addition to presence of high significant decrease in lymphocyte cells and significant decrease in monocyte cells. Serum biochemical analysis of infected animals showed that a very highly significant increase in serum sialic acid , adenosine deaminase activities and gamma globulin in theileria infected animals but significant increase in total globulin , alpha-globulin and transaminases, Maisa M.Gharieb .et. al., 470 (AST and ALT) , while serum levels of total bilirubin, blood urea and creatinine showed significant increase in cattle infected with Theileria annulata. The biochemical analysis showed also that a high significant decrease in serum glucose and albumin levels in infected animals. All diseased animals were isolated and treated with Butalex , Terramycin L.A. and Antoplex as general haematinic. Animals and their houses were sprayed for ticks using Butox. Compete recovery of diseased animals after treatment with marked improvement in haematological and biochemical parameters towards its normal levels were occurred.