Pinealectomy was performed on 7 calves, and a sham operation was performed on 3 calves. Two pinealectomized calves died immediately. The 5 remaining pinealectomized and 3 sham-operated control calves are presently involved in experimental studies. The surgical technique for exposure of the pineal gland was a rectangular (rostrotentorial) craniectomy between the median line and the horn bud. Removal of portions of the frontal and parietal bones, measuring 6 cm by 4 cm, provided adequate exposure. Positioning the head was important in order to gain the best access to the pineal gland. Water deprivation, hypertonic solution, elevation of the head, and hyperventilation prevented brain edema during the operation. The dura mater was sutured and glucocorticoids were administered to prevent postsurgical brain edema. Bone graft or plate was not placed over the craniectomy site. The soft tissue flap was repositioned over the dura mater and sutured in place--the periosteum and muscle comprising 1 layer and the skin a 2nd layer. Postsurgical complications were observed only in the 2 calves which died and were the result of hemorrhage and leukomalacia.