Concentration of monoclonal antibodies raised in mice against Brucella melitensis 16 M has been made. These monoclonal antibodies reacted only with Brucella species and not with other genera of Gram-negative bacteria. The monoclonal antibodies had been conjugated with horse radish peroxidase in order to use in the competitve Enzyme Immunosorbent Antibody (C ELISA) for the serological diagnosis of brucellosis in cattle and sheep. Fifty four and 38 serum samples were collected from cattle and sheep with previous history of brucellosis. The samples were tested with the c ELISA and the ROSE Bengale test. The percentage of positive with c ELISA were 74% and 76.3% for cttle and sheep respectively, while the percentages of positive cases with Rose Bengale test were 53.07% and 68. 3% for cattle and sheep resp < /strong>ectively. The specificity percent of the CELISA was 97.6% and the test was found to be very sensitive to detect very small amounts of antibodies in the sera. The competitive ELISA test can be used for the eradication program for brucellosis as it is very sensitive and specific for such purpose.