The morphological changes in the region of the reticulum were examined ultrasonographically in 26 cows with traumatic reticuloperitonitis, and a radiograph of the reticulum was also taken. The ultrasonographic examination included observations of reticular motility during a three minute period, of reticular contours and of adjacent structures such as the diaphragm, the anterior dorsal blind sac of the rumen, the ventral sac of the rumen, the spleen, omasum, abomasum and liver. In cows with disturbed reticular motility, biphasic contractions were slower than normal or indistinct, and the number of contractions was reduced. Fibrinous changes appeared as echogenic deposits, sometimes accompanied by hypoechogenic fluid. Abscesses had an echogenic capsule with a hypoechogenic centre. In seven cows, there was an effusion in the region of the reticulum in addition to the morphological changes. The spleen was involved in the adhesions in four cows, the omasum in three cows, the liver in one cow and the abomasum in one cow. Radiography revealed foreign bodies penetrating the reticulum of 12 cows and magnets in the reticulum of seven cows. None of these foreign bodies or magnets could be visualised by ultrasonography