1. 1. With the use of hypothermia and perfusion, 63 canine kidneys were stored for 24 hours and reimplanted. Ten excreted enough urine to prolong life, and 4 of these maintained life for 2 or more months. 2. 2. These 4 “best” kidneys were perfused with 1 part plasma or serum in 4 parts salt solution (Ringer's or Hanks'). 3. 3. Three dogs were lively 5, 14, and 14 months after removal of their normal kidney, being maintained by their stored kidney.