Electron microscope studies were carried out on the ultrastructural changes in the testis and the epidiymis of rams affected with infectious epididymitis, manifesting a pronounced clinical picture. The following conclusions were drawn: 1. The changes in the seminiferous tubules are characterized by a strongly expressed sensitivity of the cells at all levels. Noticeable are disturbances in the normal structure of the nuclear substance of both spermatogonia and spermatocytes, vacuolation of the nucleus and the cytoplasm, disrupture of the nuclear and cell membranes, decapitation of spermatids and spermatozoa with expressed lysis phenomena, and free lipid drops in the lumen. 2. The ultrastructural changes in the epididymis tubules resemble those in the seminiferous tubules: degeneration and desquamation of the ciliated epithelium, occasional disrupture of the basal membrane, and hemorrhages. The cell content of the lumen, beside the presence of pathologic spermatozoa, is admixed with leukocytes and Brucella ovis cells.