It is established that peritoneal reabsorption of 1 kidney’s excretion after uretero-peritoneostomy does not result in a compensatory increase in renal mass. To test whether a factor in normal urine which is deactivated by passage through the liver becomes renotrophic if absorbed directly into the systemic blood, either unilateral uretero-peritoneostomy or intraperitoneal infusion of normal urine was performed in rats with prior porto-caval shunts. No significant growth occurred in the intact kidney(s) of such rats. Uninephrectomy did cause compensatory hypertrophy in porto-caval rats. Thus the porto-caval shunt did not alter the inability of peritoneal urine to induce compensatory hypertrophy in spite of the obvious added excretory load.