An indirect enzyme linked immunosorbent assay (1-ELISA) to detect antibodies against Brui:ella ovis was developed and standardized. The study was carried out at the Microbiology Laboratory of the Faculty of Veterinary Medicine, San Marcos University. A hot saline extract of a Brucella ovis strain was isolated from a ram with clinical epididymitis and prepared. The assay was validated using sera from 74 rams suffering from epididymitis and confirmed by bacteria! isolation, as well as negative sera from 75 uninfected rams. The following standard parameters were established: a) polysterene microplates with flat bottomed wells, b) conjugate (rabbit immunoglobulin anti sheep IgG-peroxidase) dilution of 1: 2000, c) antigen dilution of 1: 400, and d) serum dilution of 1: 200. The maximal intraplate and interplate coefficient of variation (CV) values were 16.7% and 15.9%, respectively. Receiver-operator characteristic (ROC) analysis indicated a cutoff value of 23.89. The application of this value to both the positive and negative sera I-ELISA values yielded a diagnostic sensitivity of 97.3% anda diagnostic specificity of98.6%, with a 95% confidence interval of90.6-99.6 and 92.8-99.8, respectively. It is concluded that this validated assay provides a useful altemative for the diagnosis of ovine brucellosis.