Hypophysectomy was performed on adult male and female dogs by using the buccal approach. The left kidney which was removed through a midline abdominal incision served as a control, and the ureter of the right kidney was transplanted to the duodenum. The remaining kidney was removed 3-14 days later, and its wt. and cytologic structure were compared with those of the control kidney. The remaining kidneys of the nonhypophysectomized dogs weighed an avg. of 106% more than the control kidneys. This is in contrast to 25.15% avg. increase in the wt. of the remaining kidneys over the control kidneys of the hypophysectomized dogs.