SUMMARY Balances of sodium, potassium, and water were studied in the growing male pig as hypertension developed in response to subcutaneous implantation of deoxycorticosterone acetate (DOCA). Serum sodium, potassium, deoxycorticosterone (DOC), aldosterone, and plasma renln actirity (PRA) were determined. These variables were observed in a total of 10 experimental and nine control pigs. All animals were uninephrectomized and fed a diet of Purina Pig Chow and tap water ad libitum. No salt was added to the food or water. Serum DOC levels rose dramatically on the day of the implantation, then gradually declined but remained approximately 10 times greater than control levels 40 days after Implant.