1. A rapid fall in plasma renin concentration occurs not only in colonectomized but also in hepatectomized dogs after binephrectomy.
2. In the anhepatic anephric dog no renin extraction can be demonstrated across lungs, splanchnic region, spleen, inferior limb and head.
3. No renin inactivation occurs in blood kept in vitro at 37°C for 3 h taken from anaesthetized dogs and from the anhepatic anephric dogs.
4. We suggest that the clearance of renin in the anhepatic anephric dog is due to extraction or inactivation of renin by tissues in general.